PATRICK E. HIGGINBOTHAM, Circuit Judge:
Under the Individuals with Disabilities Education Act and its implementing regulations, parents who disagree with a school district’s evaluation of their child may be entitled to an independent educational evaluation (IEE) at public expense. The parents of Seth B., a child who had previously been diagnosed with autism, asked the Orleans Parish School Board for such an evaluation. After the board assented, Seth’s parents obtained the IEE and sought reimbursement. The school board denied their request on the ground that the IEE did not conform to state criteria. A state administrative hearing officer and the district court subsequently ruled that reimbursement was not warranted. We vacate and remand.
I
The Individuals with Disabilities Education Act (IDEA) seeks “to ensure that all children with disabilities have available to them a free appropriate public education.” 1 To this end, it establishes a process by which school districts and parents collaborate to develop individualized education programs for students with disabilities. As part of this process, school districts evaluate children to assess any disabilities and determine their educational needs.2 The IDEA and its implementing regulations also afford the parents of a child with a disability the right to an independent educational evaluation (IEE) at public expense.3 To be eligible for public funding, an IEE must meet the same criteria used by the school district in its evaluation, “to the extent those criteria are consistent with the parent’s right to an independent educational evaluation.”4
Seth B. attended public school in New Orleans. He had been diagnosed with autism and was identified as a child with a disability under IDEA. In August 2011, Seth’s parents sent the Orleans Parish School Board (OPSB) a request for an IEE. The board granted the request, offering reimbursement up to $3,000 on condition that the IEE comply with Louisiana Bulletin 1508.5 Bulletin 1508 contains the [966]*966state-mandated evaluation criteria for learning disabilities, and OPSB, like all other Louisiana public school authorities, applies Bulletin 1508 in its evaluations. The district provided a list of qualified evaluators and a link to a digital version of Bulletin 1508.
After some correspondence with the board concerning the $3,000 cost cap, Seth’s parents engaged Dr. Patricia Brock-man to produce Seth’s IEE. In April 2012, they sent OPSB Dr. Brockman’s report. OPSB responded the next month with a letter outlining 31 ways in which the IEE allegedly did not meet Bulletin 1508 criteria. The board invited Seth’s parents to have Dr. Brockman contact them to discuss the alleged areas of noncompliance. The parents did not reply to this letter, and there is no indication that Dr. Brock-man ever contacted the board. However, Seth’s IEE was discussed in an administrative hearing, ongoing at this time, concerning whether Seth was receiving a free appropriate public education.
On December 26, 2012, several months after OPSB sent its objections, Seth’s parents sent the board invoices from the IEE totaling $8066.50 and requested reimbursement. The board allegedly did not receive the request until January 31, 2013. On February 28, it denied the request in a letter to Seth’s parents, noting that it could not reimburse them for a noncompli-ant evaluation and that some of the invoices appeared unrelated to the completion of the IEE.
In April 2013, Seth and his parents requested an administrative due process hearing.6 An ALJ heard preliminary arguments from counsel from both sides. On August 14, 2013, he ruled against Seth and his parents, finding that their counsel had stipulated to the IEE’s noncompliance with Bulletin 1508 and that he therefore lacked jurisdiction to award reimbursement.
Seth and his parents sought review in federal district court pursuant to the IDEA.7 The district court received affidavits, exhibits, and depositions and heard oral argument, but did not allow a full trial on the merits. Rather, on January 20, 2015, it granted summary judgment for OPSB. The court found that the board had not waived its right to challenge Seth’s IEE, that the IEE did not comply with Bulletin 1508, and that reimbursement was therefore disallowed.
This appeal followed. The Council of Parent Attorneys and Advocates, Inc., the National Disability Rights Network, the National Federation of the Blind, and the National Association of the Deaf filed ami-cus briefs urging reversal. The National School Boards Association, the National Association of State Directors of Special Education, and school board associations from Louisiana, Mississippi, and Texas filed an amicus brief urging affirmance.
II
Under 20 U.S.C. § 1415(i)(2)(C), which formed the basis for this action, a district court must (i) “receive the records of the administrative proceedings”; (ii) “hear additional evidence at the request of a party”; and (iii) base “its decision on the preponderance of the evidence” and “grant such relief as the court determines is appropriate.” The district court is required to “accord ‘due weight’ to the hearing officer’s findings,” but it “must ultimately reach an independent decision based on the preponderance of the evidence.”8 [967]*967Thus, “the district court’s ‘review1 of a hearing officer’s decision is ‘virtually de novo.’ ”9 Accordingly, in IDEA proceedings, summary judgment “is not directed to discerning whether there are disputed issues of fact, but rather, whether the administrative record, together with any additional evidence, establishes that there has been compliance with IDEA’S processes and that the child’s educational needs have been appropriately addressed.”10
We have never articulated the standard of review for the appeal of a district court’s determination that an IEE does not merit reimbursement. Plainly, however, the district court’s inquiry was one of both fact and law, in that the court both interpreted the requirements of federal and state educational regulations and analyzed whether appellants’ IEE and the board’s conduct conformed to those requirements. “Mixed questions should be reviewed under the clearly erroneous standard if factual questions predominate, and de novo if the legal questions predominate.” 11 Here, the validity of the district court’s ruling turns in large part on the interpretation of regulatory text. We therefore review the ruling de novo.12 Within this analysis, however, we review the district court’s underlying factual findings for clear error.13
Ill
We first consider whether OPSB waived its right to refuse reimbursement. Appellants and amici contend that it did, both because the board failed to initiate a hearing to contest Seth’s IEE and because it unnecessarily delayed in complying with its duties under IDEA’S implementing regulations. We disagree.
1. Initiation of the due process hearing
Disputes over IEE reimbursement are governed by an implementing regulation of the IDEA, 34 C.F.R. § 300.502, which reads in relevant part:
(b) Parent right to evaluation at public expense.
[•••]
(2) If a parent requests an independent educational evaluation at public expense, the public agency must, without unnecessary delay, either—
[968]*968(i) File a due process complaint to request a hearing to show that its evaluation is appropriate; or
(ii) Ensure that an independent educational evaluation is provided at public expense, unless the agency demonstrates in a hearing pursuant to §§ 300.507 through 300.513 that the evaluation obtained by the parent did not meet agency criteria.14
In this case, after appellants requested an IEE at public expense, OPSB neither requested a hearing to show that its own evaluation was appropriate, nor did it request a hearing to show that appellants’ evaluation failed to meet relevant criteria. Rather, appellants requested a hearing on the subject of reimbursement. They now claim that the regulation required OPSB to request a hearing, and that by failing to do so, the board waived its right to refuse reimbursement.
The plain text of the regulation contradicts appellants’ reading. § 300.502(b)(2)(h) excuses an agency from paying for an IEE if the agency simply “demonstrates in a hearing ... that the evaluation obtained by the parent did not meet agency criteria.” 15 It does not require the agency to “initiate” or “request” the hearing. In contrast, under (b)(2)(i), the agency must “file” a complaint and “request” a hearing if it wishes to decline reimbursement on the ground that its own evaluation was appropriate. This distinction strongly favors reading § 300.502(b)(2)(ii) not to require the agency to initiate a hearing.16
Appellants and amici. refer us to Department of Education commentaries suggesting that § 300.502(b)(2)(ii) gives a school district the duty to initiate a hearing in this context. This contradicts the unambiguous text of the regulation. “If [a] regulation is unambiguous, we may ... consider agency interpretation, but only according to its persuasive power.” 17 The most squarely relevant commentary cited, a 2001 opinion letter, states that if an IEE does not comply with district cost criteria, “[t]he public agency must, without unnecessary delay, initiate a hearing to demonstrate that the evaluation obtained by the parent did not meet the agency’s cost criteria.” In so opining, however, the Department was responding to school district policies purporting to exercise “sole judgment” over the issue of compliance.18 Its statement that the districts might be required to “initiate” hearings was incidental to its broader point that they could not legally claim “sole judgment.”19 Perhaps [969]*969not coincidentally, the letter does not engage in any detail with the text of § 300.502(b)(2).20 We find this guidance of questionable value and opt instead to follow the clear text of the regulation itself.
Appellants and amici also cite several out-of-circuit cases in support of their reading of § 300.502(b)(2)(ii). We find these cases unpersuasive. In Evans v. District No. 17, the Eighth Circuit required a school district to reimburse parents for the cost of their IEE because the district never “initiated a hearing ... to show the inappropriateness of the [parents’] evaluation, or to show that its evaluation [was] appropriate.”21 That holding turned on an earlier version of § 300.502(b) that (unlike the current version) did not explicitly contemplate a district’s refusal to reimburse for reasons of noncompliance with relevant criteria, or distinguish between such a refusal and a refusal based on the adequacy of the district’s own evaluation.22 The same is true of a subsequent Seventh Circuit case cited by appellants.23 More recently, in an unpublished opinion, the Eleventh Circuit held without explanation that, because a school board had failed to file a due process request challenging parents’ IEE under either § 300.502(b)(2)(i) or § 300.502(b)(2)(h), the parents were entitled to reimbursement.24 The decision does not examine the text of the regulation in any detail and appears to elide the clear distinction in the wording of the two clauses at issue. These deficiencies are also present in various lower court decisions [970]*970cited in the briefs.25
In sum, neither the plain text of the regulation nor binding precedent required OPSB to initiate a hearing in order to contest appellants’ right to'reimbursement. This result conforms with the broader purpose of § 300.502(b), that is, to ensure parents’ rights to an IEE at public expense and to due process in the event of a reimbursement dispute. These rights can be vindicated just as well in a hearing initiated by the parents as in one initiated by a school district, as the Sixth Circuit recognized in P.R. v. Woodmore Local School District.26 In that case, the court held that § 300.502(b)(2)(i) was not violated when a school board objected to an IEE by defending the appropriateness of its own evaluation in a due process hearing initiated by the parents. The court reasoned that the “object” of the regulations “is to afford Parents an opportunity to challenge and the School District to defend the appropriateness of its Evaluation in an impartial hearing,” which had occurred. It continued:
As long as the object of the regulations is accomplished, there is no reason to exalt form over substance. Their purpose is not served by holding that there must be reimbursement at public expense when it is the parents rather than the public agency that initiates the due process hearing where the appropriateness of the School District’s Evaluation is challenged and confirmed.27
The Sixth Circuit’s insight applies with even greater force in the context of § 300.502(b)(2)(ii), whose plain text — unlike that of (b)(2)(i) — does not require the agency to initiate a hearing.
2. Timeliness
OPSB did not have to initiate a hearing in order to preserve its objection to Seth’s IEE. This is not to say, however, that the board could wait indefinitely, forcing appellants to either demand a hearing or forsake reimbursement. Rather, under § 300.502(b)(2)(ii), OPSB had to “demonstrate” the IEE’s noncompliance with relevant criteria “without unnecessary delay.” We find that OPSB fulfilled this duty.
Appellants sent the board an e-mail on August 25, 2011, stating that “we are requesting an Independent Educational Evaluation for our son Seth____ Seth is entitled to receive a comprehensive IEE at public expense.” However, the record indicates that appellants did not submit invoices until over a year later. Only then could OPSB know with certainty that appellants sought an IEE at public expense28 —especially since for much of that périod, appellants knew of the board’s objections to the evaluation, but took no apparent action to address them.29 We see no rea[971]*971son to penalize OPSB for failing to preemptively seek a hearing on the topic of reimbursement when appellants had not actually requested reimbursement, and when the board had reason to believe they might not. Rather, on these specific facts, the board’s delay in “demonstrating” the IEE’s noncompliance should be measured from the submission of the invoices.
Appellants’ invoices accompanied a letter dated December 26, 2012, which OPSB claims it did not receive until January 81, 2013.30 Roughly three months later, on April 30, 2013, appellants requested an IDEA due process hearing. From this point, any further delays were a function of the administrative process, not OPSB’s sole inaction.31 Depending on whose records are credited, then, either three or four months passed during which OPSB reasonably could have moved to “demonstrate” the IEE’s noncompliance, but did not. We will consider this period in determining whether OPSB acted “without unnecessary delay.”
At the outset, we observe that there is little case law or regulatory guidance speaking directly to this question. Appellants and amici cite numerous rulings of lower courts and state agencies, but most of these rulings appear to involve school districts failing to timely respond to parents’ initial requests for IEEs “without unnecessary delay.” Thus, in many of the cited cases, upon receiving a parent’s IEE request, the school district took no action — neither granting the request, nor filing for a due process hearing to demonstrate the adequacy of their own evaluation.32 In others, after receiving an IEE request, the school district waited three months or longer to request a due process hearing to show the adequacy of its own evaluation.33
These cases provide limited guidance in the case before us, in which the board delayed not in responding to or challenging parents’ initial IEE inquiry, but in contesting their right to reimbursement after the IEE had been completed.34 When a parent first requests an IEE, the school placement or educational plan for the child may be contingent on the outcome of the IEE. A months-long delay before even starting the process of holding a due process hearing on the need for an independent evaluation is a significant amount of time when compared to the length of the school year. In contrast, [972]*972once the IEE has been completed, school officials can consider it immediately before reimbursement issues are resolved. Thus, the IEE’s function is not vitiated when only reimbursement is delayed.
To be sure, keeping parents waiting for three or four months before action is taken on reimbursement may be a significant burden, considering the cost of IEEs. But such a delay does not have the same effect (or even any effect) on a child’s educational plan as failing to take action on an initial request for an IEE does. Here, any delay by OPSB did not affect whether the IEE could be considered in relation to Seth’s schooling plan.35 We also note that during the period at issue, OPSB explained its bases for denying reimbursement in a detailed letter to appellants and urged them to contact the board with any questions. Arguably, this letter was an attempt to informally resolve the dispute.36 In light of these facts, we conclude that OPSB did not “unnecessarily] delay” in “demonstrating” the IEE’s noncompliance.
IV
We next consider whether appellants were denied their procedural rights in the district court proceeding. Appellants contend that the district court improperly placed the burden of persuasion on them. The district court reasoned that “the burden of persuasion [should] fall[] where it usually does, on the party seeking relief.” Appellants argue that the typical presumption should not apply in IEE reimbursement disputes, since 34 C.F.R. § 300.502(b)(2)(h) requires the agency, not the parents, to “demonstrate” noncompliance with relevant criteria. However, this requirement applies only to administrative due process hearings.37 § 300.502(b)(2)(h) does not purport to govern the appeal of an hearing officer’s decision to the federal district court. Rather, such an appeal arises under the IDEA’S procedural safeguards provision.38 As the court below noted, several circuits have interpreted this provision to place the burden of persuasion before the district court on the party appealing an IDEA hearing officer’s decision.39 This result conforms to “the ordinary default rule that plaintiffs bear the risk of failing to prove their claims.”40 The district court sensibly followed this default rule, and did not err in allocating appellants the burden of persuasion.
[973]*973Appellants further argue that the district court erred in refusing to hold an evidentiary hearing with witnesses. Although such a hearing might have been helpful, it was not required in this case. IDEA gives any party aggrieved in a due process hearing “the right to bring a civil action” in a federal district court without regard to the amount in controversy. The district court must both “receive the records of the administrative proceedings” and “hear additional evidence at the request of a party.”41 Whether this latter phrase requires a district court to hold an evidentiary hearing where witnesses testify and are cross-examined is apparently an issue of first impression. Certainly, however, the text itself does not require such a hearing.42 And the district court did not decide the case on the basis of the administrative record alone. On the contrary, it received additional evidence in the form of exhibits, affidavits, and depositions, and it held oral argument on the motion for summary judgment. We thus conclude that the district court did not fail to “hear additional evidence.”43
V
Having determined that OPSB did not waive its right to refuse reimbursement and that the proceedings before the district court were procedurally sound, we approach the crux of this dispute: whether appellants’ IEE failed to “meet agency criteria,” precluding reimbursement.44 Before considering whether Seth’s IEE complied with Bulletin 1508’s criteria, we must determine the criteria relevant to that inquiry. Appellants argue that many of the IEE’s 31 alleged nonconformities are illusory because they relate to criteria that were never legally applicable to Seth’s IEE in the first place.45 Their argument has several facets.
First, appellants contend that OPSB may only apply criteria “employed at the initiation of an evaluation,” and not “eon-tent-based” criteria. They cite 34 C.F.R. § 300.502(e)(1), which provides that “[i]f an independent educational evaluation is at public expense, the criteria under which the evaluation is obtained, including the location of the evaluation and the qualifications of the examiner, must be the same as the criteria that the public agency uses [974]*974when it initiates an evaluation.”46
Appellants do not explain how to distinguish “initiation” criteria from “content-based” criteria. Moreover, the phrase “when it [i.e., the agency] initiates an evaluation” could plausibly be understood to identify the evaluations relevant to determining criteria applicable to IEEs, not to limit those criteria. In other words, the regulation can be read to simply subject IEEs (i.e., evaluations initiated by parents) to the same criteria as agencies’ own evaluations (i.e., evaluations initiated by agencies). Nonetheless, appellants’ reading— that the phrase is language of limitation, not identification — is also plausible as a purely textual matter.47
When confronted with ambiguity in regulatory text, we look to agency interpretations.48 In comments on § 300.502(e), DOE has explained that IEEs must meet substantive requirements applicable to school-conducted evaluations:
We do not believe it is necessary to add language to the regulations regarding the review of existing data, input from the child’s parents, the scope of the evaluation, or the instruments used to evaluate the child, because an IEE must meet the agency criteria that the public agency uses when it initiates an evaluation. ... Similarly, [the IDEA regulations] provide!] that an evaluation conducted by a public agency must use a variety of assessment tools and strategies to gather relevant functional, developmental, and academic information about the child, including information provided by the parent, that may assist in determining whether the child is a child with a disability.... These requirements also apply to an IEE conducted by an independent evaluator, since these requirements mil be a part of the agency’s criteria,49
This interpretation is consistent with IDEA’S underlying purposes.50 It would seem perverse to enforce non-substantive criteria such as those pertaining to an evaluation’s location, but wholly exempt IEEs from substantive criteria concerning, for example, valid assessment strategies and reporting methods. As the Supreme Court has noted, Congress wrote extensive [975]*975procedural safeguards into IDEA in part to ensure substantively sound educational outcomes.51 A rule wholly exempting IEEs from substantive criteria would diminish the rigor of the IDEA process, with attendant heightened risk of compromised results. Appellants’ “initiation” argument thus fails.
Second, appellants appear to argue that Bulletin 1508’s criteria, including those that require a multidisciplinary team, are generally inapplicable to an IEE because that document is oriented toward schools and does not address IEEs in detail.52 This argument also fails. Under § 300.502(e)(1), IEEs must use the same “criteria that the public agency uses.” The public agency in this case, OPSB, uses Bulletin 1508, and the Bulletin therefore applies to the IEE.
Third, appellants claim that only the portions of the IEE relating to their areas of disagreement with the board had to comply with Bulletin 1508 criteria. They invoke DOE guidance allowing an IEE to be limited to the scope of disagreement between parents and an agency. Perhaps, but this guidance does not directly address reimbursement.53 OPSB cites an August 2011 letter from appellants, in which they stated that “Seth is entitled to receive a comprehensive IEE at. public expense,” as evidence that they implicitly agreed to be bound by the criteria applicable to all evaluation components. Appellants dispute whether this was really a request for a comprehensive IEE and whether “comprehensive” has any ascertainable legal meaning here. We see no need to wade into this debate. Under 34 C.F.R. § 300.502(b) and (e), a school board has no duty to pay for an IEE demonstrated not to meet agency criteria. Here, appellants claim reimbursement for the entire IEE, so the entire IEE must meet Bulletin 1508’s criteria to the extent those criteria are otherwise applicable. This is true whether or not portions of the IEE relate to areas of agreement, and regardless of any intentions the parents may have previously expressed.54
Fourth, appellants claim that Seth’s IEE was a reevaluation, not an initial evaluation, and that initial evaluation criteria are therefore inapplicable. In[976]*976deed, many of the IEE’s 31 alleged non-conformities. derive from Bulletin 1508 criteria that apply to initial evaluations.55 Even assuming the IEE was a reevaluation,56 we nonetheless find that initial evaluation criteria were applicable. The district court found that appellants suspected Seth had a previously undiagnosed learning disability.57 Under Bulletin 1508, this required them to comply with initial evaluation criteria.58
Fifth, and finally, running through appellants’ briefs is the underlying contention that Bulletin 1508 is so onerous as to cumulatively and inherently violate parents’ right to an IEE.59 We cannot agree. The Bulletin 1508 criteria at issue, although extensive, address the quality and thoroughness of evaluations. This is not a case, for example, where agency criteria effectively allow only agency employees to conduct IEEs, constraining parents and undermining the independence of evaluations without necessarily advancing the goal of rigor.60 Allowing parents to ignore Bulletin 1508’s criteria can complicate subsequent efforts to compare the IEEs to the districts’ own evaluations, undermining a key function of the IEE. Moreover, much of the burden of compliance in this case appears related to appellants’ unique circumstances.61 In light of these circumstances, appellants might have sought to limit the scope of their IEE, and thereby avoid triggering some criteria, before obtaining the evaluation, whether in negotiation with OPSB or in an IDEA due process hearing.62 Instead, they obtained a lengthy IEE that implicated many Bulletin 1508 criteria. Under § 300.502(b) and (e), the IEE had to meet those criteria to merit reimbursement.
We do not doubt that Bulletin 1508 imposed a heavy burden in this case. In[977]*977deed, the record suggests that Seth’s parents faced an uphill battle in deciphering its criteria and locating and assembling the requisite evaluators. Despite their diligence and willingness to spend thousands of dollars, they were unable to produce a perfectly compliant IEE. The record also indicates that OPSB — which had a “ ‘natural advantage’ in information and expertise” in this context63 — could have been more helpful in explaining the relevant requirements and processes.64 Although these facts give us pause, for the reasons we have offered, we cannot conclude that the application of Bulletin 1508 violated the right to an IEE in this specific case.
VI
The Bulletin 1508 criteria implicated in OPSB’s 31 alleged areas of noncompliance apply to Seth’s IEE. We may therefore consider whether the IEE complies with those criteria. As we have noted, the ALJ below resolved this question against appellants, apparently on the basis of an alleged stipulation as to the IEE’s noncompliance. Appellants deny that they so stipulated, and the record is ambiguous as to this point.65 Nonetheless, in a subsequent filing with the district court, appellants wrote: “Plaintiffs admit that the IEE obtained by them does not contain some elements or components required by Louisiana Bulletin 1508 criteria. Nevertheless, Plaintiffs submit that the information contained in the IEE substantially complies with the Bulletin 1508 criteria.”
The district court upheld the ALJ’s noncompliance finding. It did not address appellants’ argument that the IEE was substantially compliant. Rather, citing the ALJ’s finding and OPSB’s recital of the 31 alleged areas of noncompliance, it simply held that “the parties agree that the IEE obtained by Plaintiffs does not meet Bulletin 1508 criteria” and that “Plaintiffs are not entitled to reimbursement because the IEE at issue does not comply with Bulletin 1508 criteria.”
The degree of compliance necessary for an IEE to “meet agency criteria” under 34 C.F.R. § 300.502 is not explicitly defined in IDEA, its implementing regulations, or the case law, nor is there any directly relevant agency guidance. Yet standards akin to substantial compliance are already deployed in other IDEA contexts.66 For example, we consider substantial compliance in determining whether school districts have provided education “in conformity with” students’ individual[978]*978ized education programs (IEPs), as IDEA requires.67
We are persuaded that substantial compliance also suffices in the IEE context. 34 C.F.R. § 300.502 nowhere demands perfect adherence to agency criteria.68 Indeed, such a requirement is in tension with core purposes of the right to an IEE and of the IDEA generally.
As the Supreme Court has emphasized, IDEA’S procedural safeguards, including the right to an IEE, are essential to the statutory scheme.69 Through them, Congress sought to “giv[e] parents and guardians a large measure of participation at every stage of the administrative process,”70 and to ensure that the process produced substantively sound results.71 The right to an IEE at public expense serves these purposes, both because it enables parents to genuinely and consequentially take part in the IDEA process and because it allows them to introduce additional and different data into that process, informing its ultimate outcomes.72
A substantial compliance standard for IEE reimbursement also advances these purposes. First, it safeguards parents’ ability to participate in the IDEA process through IEEs by preserving a realistic possibility of reimbursement. The state criteria that govern IDEA evaluations can be complex. Given this, and given their “natural advantage in information and expertise” in this context,73 school agencies [979]*979may be able to find ambiguities or inconsequential nonconformities in any IEE. If they are allowed to deny reimbursement in turn, they will effectively be able to treat parents’ right to an IEE as a privilege to be granted at their discretion, since few parents can afford to spend thousands of dollars out of pocket on an evaluation. Second, by ensuring reimbursement for generally sound IEEs that may happen to be deficient in isolated or trivial ways, a substantial compliance standard will encourage parents who might not otherwise have obtained and submitted IEEs to do so, leading to better-informed IDEA outcomes.
The board worries that “[i]f this Court were to adopt the Plaintiffs’ implicit criterion of “substantial” compliance____ [b]ased on an unreasonably low standard, presumptively a couple of paragraphs — or even a prescription pad with ‘OHI,’ ‘Autism,’ or ‘SLD’ with little more — would suffice as an IEE.” Although the slippery slope is always a concern when the law accepts less-than-perfect compliance,74 we find the risk acceptable here, given the strong statutory interests favoring a substantial compliance standard and the use of such standards elsewhere in the IDEA case law. We do not suggest that “a couple of paragraphs” or a “prescription pad” notation will now pass muster. Indeed, the determination will necessarily turn on the particular facts and agency criteria at issue in each case. “Substantial compliance,” allowing reimbursement in this context, means that insignificant or trivial deviations from the letter of agency criteria may be acceptable as long as there is substantive compliance with all material provisions of the agency criteria and the IEE provides detailed, rigorously produced and accessibly presented data.
In so holding, we are mindful of our limited expertise.75 To be sure, a substantial compliance standard presumes that adjudicators can reliably identify which deviations are “substantial,” requiring some engagement with substantive questions of special education practice. Yet this is nothing new. IDEA already requires district courts to review the factual findings of administrative hearing officers “virtually de novo.”76 In turn, they must “reach ... independent conclusion^] based upon the preponderance of the evidence” 77 as to such questions as whether students require more or less restrictive learning environments,78 whether IEPs are “reasonably calculated to enable [children] to receive educational benefits,”79 and whether schools’ failures in implementing IEPs implicate “significant provisions of ... IEP[s]” or are instead “de minimis.”80 Seeing “substantial compliance” as a comfortable fit within a regi[980]*980men constructed to promote exchange and cooperative engagement for the benefit of student and school, we doubt applying a substantial compliance standard to IEEs will pose a greater' challenge, or stretch courts’ role farther than the statute itself contemplates.
VII
Seth’s IEE will “meet agency criteria” and merit reimbursement if it substantially complies with Bulletin 1508. As noted above, the district court did not squarely address this factually specific question. We therefore remand for analysis under a substantial compliance standard. If the court below (or, upon further remand, the administrative hearing officer) finds the IEE substantially compliant, it should award reimbursement.
In any event, however, appellants will not be entitled to the full cost of the evaluation they obtained. Appellants knew of OPSB’s $3,000 cost cap for IEEs, yet they spent over $8,000. The Department of Education has explained that IDEA allows schools to enforce reasonable cost criteria for IEEs as long as parents in unique circumstances have the opportunity to request exemption.81 Here, OPSB offered appellants an opportunity to demonstrate unique circumstances in its correspondence with them over the cost cap, but appellants. did not respond. Therefore, the $3,000 cap binds them.82
We VACATE and REMAND to the district court for further proceedings consistent with this opinion.