Peters, C. J.
These appeals are a sequel to Horton v. Meskill, 172 Conn. 615, 648-49, 376 A.2d 359 (1977) (Horton I), in which this court held unconstitutional the then existing statutory financing system for free public elementary and secondary school education in this state. Noting the difficulties of formulating appropriate orders of relief, we agreed in Horton I with the trial court’s decision to retain jurisdiction while the General Assembly was afforded an opportunity to take responsive legislative action. Id., 650-53. The legislature in 1979 enacted, and in subsequent years amended, a plan intended to achieve equity in educational financing. Public Acts 1979, Nos. 79-128,79-553; see General Statutes §§ 10-76f, 10-76g; §§ 10-261 through 10-263a; §§ 10-266m through 10-280a. The present litigation is a challenge by the original plaintiffs in Horton I and certain intervenors1 to the constitutionality of the new plan, [27] both as originally enacted and as subsequently amended. The principal issue is whether this plan now provides the substantially equal educational opportunity for all Connecticut public school children that the Connecticut constitution requires. The trial court, Spada, J., after extensive hearings, rendered judgments holding the plan constitutional in design but unconstitutional in part. The defendants have appealed and the plaintiffs have cross appealed. We find error in part on the appeal only.
The trial court examined in detail the provisions of the educational equity plan that the General Assembly enacted in 1979; Public Acts 1979, No. 79-128; and [28] subsequently modified. That plan has two principal components: (1) the guaranteed tax base grant formula (GTB) and (2) the minimum expenditure requirement (MER). The GTB formula is a plan of state grants designed to provide towns with a state-guaranteed tax base for the financing of public school education.2 It is designed to distribute equitably state aid to towns that establish their eligibility through the MER, a formula that sets the minimum acceptable level of per [29] pupil town expenditures.3 The 1979 act did not commit any of the participants to immediate full implementation. Both state funding and local MER payments were to be phased-in over a five year period. In addition, property-poor towns were protected by a temporary “alternate” MER, which gave them access to GTB grants on the basis of their historical record of educational financing.4 Finally, all towns were guaran[30] teed minimum-aid grants of $250 per pupil. The court concluded that this basic plan for financing of public school education provided a constitutionally appropriate mechanism to reduce state-wide disparity in educational resources. The court also found constitutional the state programs for equitable disbursement of categorical grants for transportation, special education and school construction. See General Statutes §§ 10-266m through 10-280a; §§ 10-76f, 10-76g; and §§ 10-282 through 10-292.
The court nonetheless concluded that the salutary effect of these constitutional programs is being undermined by post-1979 destabilizing legislative action which has repeatedly postponed full implementation of the GTB program. The court thus declared unconstitutional: (1) the statute providing for continued minimum aid grants of $250 per pupil, regardless of town need; General Statutes § 10-262c (f) as amended;5 (2) the statute requiring use of three year old data in the calculation of the guaranteed tax base; General Statutes § 10-261 (a) as amended;6 (3) the statute postponing full funding of the guaranteed tax base to a seventh year; [31] General Statutes § 10-262c (c) as amended;7 and (4) the statute permitting towns to measure their minimum expenditure requirement (MER) by an alternate standard short of full funding; General Statutes § 10-262e (c), (d), as amended.8 In a further [32] effort to achieve educational equity, the court concluded that the existing optional curriculum for secondary [33] school students was unconstitutional; General Statutes § 10-16b (a).9 In each instance in which the court found the existing statutes to be constitutionally flawed, it ordered those of the defendants who had implementing responsibility to take designated appropriate action.10 Despite these conclusions of unconstitutionality the court determined that, because the GTB program was basically constitutional, there was no need to hold a remedial stage hearing.11
The defendants in their appeals challenge each of the trial court’s conclusions of unconstitutionality and the procedural and substantive propriety of its remedial orders. The plaintiffs in their cross appeals principally urge us to overturn the trial court’s conclusion that the [34] GTB program is basically constitutional, and to order further remedial implementation.
Because many of the issues raised by all the appeals turn on whether the GTB program is constitutional in its basic design, we will first address that question. We will then consider the trial court’s curricular order and the amendments to Public Acts 1979, No. 79-128, which the court found to have an unconstitutional effect. To the extent that any legislative acts may be unconstitutional, we must determine whether the trial court should consider their remedial implications at a further hearing in which all the interested parties may have an opportunity to participate fully.
I
Assessment of the constitutionality of the GTB plan for educational equity enacted by Public Acts 1979, No. 79-128, must start with the constitutional standard that we laid down in Horton I. Relying on those articles of the Connecticut constitution that provide for free public education and for equal rights and equal protection,12 [35] we held that “in Connecticut the right to education is so basic and fundamental that any infringement of that right must be strictly scrutinized.” Horton I, supra, 646. We recognized, however, that the fundamental right to educational equity implicated the law of equal protection in a way that was “ ‘in significant aspects sui generis’ ” and hence could not be measured “by accepted conventional tests or the application of mechanical standards.” Id., 645; see also Campbell v. Board of Education, 193 Conn. 93, 104-105, 475 A.2d 289 (1984). In particular, we noted in Horton I that “[t]he wealth discrimination found among school districts differs materially from the usual equal protection case where a fairly defined indigent class suffers discrimination to its peculiar disadvantage. The discrimination is relative rather than absolute.” Horton I, supra, 645. We also acknowledged the general applicability of the presumption that legislative action is constitutional unless its invalidity is established beyond a reasonable doubt. Id., 650. We therefore defined the state’s constitutional obligation as a duty to allocate governmental support to education so that state funds, instead of equally benefiting all the towns by way of a flat grant, would offset the demonstrated significant disparities in the financial ability of local communities to finance local education through the local property tax. Id., 649. We held that the state was required to assure to all students in Connecticut’s free public elementary and secondary schools “a substantially equal educational opportunity.” Id.
We agree with the trial court that in light of Horton I, Public Acts 1979, No. 79-128, must be strictly scrutinized to determine whether it is constitutional. Horton I, supra, 646. However, the sui generis nature of litigation involving school financing legislation militates against formalistic reliance on the usual standards of the law of equal protection, in particular against the [36] requirement that the state must demonstrate a compelling state interest.13 See Dunn v. Blumstein, 405 U.S. 330, 335, 342, 92 S. Ct. 995, 31 L. Ed. 2d 274 (1972); Ryszkiewicz v. New Britain, 193 Conn. 589, 597, 479 A.2d 793 (1984).14
[37] In searching for an appropriate and workable standard that is consistent with the mandate of Horton I, we may fruitfully borrow a framework of analysis that federal courts have devised to assess the constitutionality of state legislative apportionment plans. The Supreme Court of the United States has acknowledged that the equal protection clause, in that context, although it requires “strict scrutiny [of] classifications bearing on the right to vote in state elections”; Plyler v. Doe, 457 U.S. 202, 233, 102 S. Ct. 2382, 72 L. Ed. 2d 786, reh. denied, 458 U.S. 1131, 103 S. Ct. 14, 73 L. Ed. 2d 1401 (1982) (Blackmun, J., concurring); see also id., 217 n.15 (opinion of the court); does not compel “the State to demonstrate that its classification has been precisely tailored to serve a compelling governmental interest.” Id., 217. The court has instead developed what is functionally a three-part test to determine whether a state has fulfilled its obligation under the equal protection clause to “make an honest and good faith effort to construct districts, in both houses of its legislature, as nearly of equal population as is practicable.” Reynolds v. Sims, 377 U.S. 533, 577, 84 S. Ct. 1362, 12 L. Ed. 2d 506 (1964); Mahan v. Howell, 410 U.S. 315, 324-25, 93 S. Ct. 979, 35 L. Ed. 2d 320, modified, 411 U.S. 922, 93 S. Ct. 1475, 36 L. Ed. 2d 316 (1973); Brown v. Thomson, 462 U.S. 835, 842, 103 S. Ct. 2690, 77 L. Ed. 2d 214 (1983). First, a plaintiff must establish a prima facie case of discrimination by demonstrating that a state’s plan results in more than “ ‘minor deviations from mathematical equality among state legislative districts . . . .’” Brown v. Thomson, supra, 842. If the plaintiff proves that the disparities are not de minimis, the burden then shifts to the state to justify them. The state must show that its plan [38] “may reasonably be said to advance [a] rational state policy . . . Brown v. Thomson, supra, 843, quoting Mahan v. Howell, supra, 328. Its justification must, of course, be “ ‘free from any taint of arbitrariness or discrimination.’ ” (Citation omitted.) Mahan v. Howell, supra, 325; see Brown v. Thomson, supra, 852 (Brennan, J., dissenting). A showing that the state’s reasons are legitimate and are in fact furthered by its plan, however, does not end the inquiry. Under the third part of the test, a plan will not withstand scrutiny if the resulting disparities are still so great as to be unconstitutional. See Brown v. Thomson, supra, 844-45; Mahan v. Howell, supra, 329.
We conclude that, like legislative apportionment plans, educational financing legislation must be strictly scrutinized using a three-step process. First, the plaintiffs must make a prima facie showing that disparities in educational expenditures are more than de minimis in that the disparities continue to jeopardize the plaintiffs’ fundamental right to education. If they make that showing, the burden then shifts to the state to justify these disparities as incident to the advancement of a legitimate state policy. If the state’s justification is acceptable, the state must further demonstrate that the continuing disparities are nevertheless not so great as to be unconstitutional. In other words, to satisfy the mandate of Horton I, a school financing plan must, as a whole, further the policy of providing significant equalizing state support to local education. Horton I, supra, 649. However, no such plan will be constitutional if the remaining level of disparity continues “to emasculate the goal of substantial equality.” Mahan v. Howell, supra, 326.
The trial court came to its ultimate conclusion that Public Acts 1979, No. 79-128, was constitutional by a route that differs from the three-part test which we [39] have decided to adopt. Nevertheless, we agree with its holding on this issue.
It is conceded by all parties that the evidence before the trial court demonstrates continued significant disparities in the funds that local communities spend on basic public education.15 The plaintiffs’ evidence therefore suffices to shift to the state the burden of justification for the statute.
W e next consider whether the state has met this burden. The trial court reasoned that the legislation enacted in 1979 was a constitutionally acceptable response to the problem of disparate local educational expenditures. The court determined that, if adequately funded, the GTB program would provide sufficient overall expenditures for public school education, that its five-year phase-in assured an efficient use of educational resources, and that its design would provide equity in the distribution of educational funds and a proper balance between state and local contributions [40] thereto. In addition, the court found that the program retained a salutary role for local choice by guaranteeing minimum funds without imposing a ceiling on what a town might elect to spend for public education. Finally the court noted that a number of factors beyond direct state control had tended, in the recent past, to increase rather than diminish discrepancies in educational spending. The trial court identified several such factors: public school enrollment has decreased more rapidly in the wealthier than in the poorer towns; property values have increased more rapidly in the wealthier than in the poorer towns; and recent high rates of inflation have eroded the benefits of the GTB grants to the poorer towns. In light of all of these circumstances, Public Acts 1979, No. 79-128, was a reasonable response to the policy dictates of Horton I.
In assessing the adequacy of the challenged state legislation under the third step of the test, we can rely on the trial court’s finding that the effect of the legislation was to narrow significantly disparities in the ability of local communities to finance local education16 and to increase significantly the state’s share of overall educational costs for public schools.17 It was, therefore, reasonable for the trial court to conclude that the remaining disparities did not undermine the basic policy of equalizing state support for education.
In agreeing with the trial court’s judgment regarding the constitutionality of the legislation as originally enacted, we also concur with the court’s judgment on the plaintiffs’ cross appeal. The plaintiffs sought to [41] impose state funding of 50 percent of overall educational expenditures as the only constitutionally adequate response to educational disparities. The trial court carefully considered that proposal and correctly decided that assigning a fixed share of expenditures to the state did not provide a sound basis for assuring a proper distribution of responsibility or of funding for substantially equal educational opportunities.
We also agree with the conclusion of the trial court that the state plan for the distribution of categorical grants is constitutional. The court found that the categorical grant programs had not been shown to impinge upon the fundamental right to a substantially equal education. The plaintiffs, who raise this issue in their cross appeals, have not pointed to any evidentiary basis in the record to contradict this finding by the trial court. They therefore have failed to establish the necessary predicate for their claim that impairment of their fundamental rights in this regard required current funding of special education grants.
II
We turn now to the appeals from the decision of the trial court declaring unconstitutional certain post-1979 statutes implementing the present state program for educational equity. The court’s judgments of unconstitutionality relate in the main to statutes that have an impact upon the continued disparities in local educational expenditures, but the court also found unconstitutional the statute which allowed local communities the option to determine the curriculum for secondary school education. General Statutes § 10-16b (a).18 We will consider these matters in reverse order.
The court ordered, on constitutional grounds, that locally determined high school curricula be replaced by [42] a state-defined core curriculum. The defendants claim that the court’s orders are invalid because the constitutionality of § 10-16b (a) was never questioned in the plaintiffs’ complaints. We need not decide whether this claim is well taken because events have overtaken the court’s orders. The court specifically foresaw such a possibility when its judgments stated that they should “not be construed to prohibit changes to the mandated core curriculum by legislative amendment.” The General Assembly has now enacted a core curriculum requirement for high school graduation. Public Acts 1984, No. 84-297.19 Since there is no longer any basis [43] for affording judicial relief on these orders, they have become moot and therefore we need not determine their validity. Connecticut Foundry Co. v. International Ladies Garment Workers Union, 111 Conn. 17, 19, 411 A.2d 1 (1979); Reynolds v. Vroom, 130 Conn. 512, 515, 36 A.2d 22 (1944).
The court’s principal determinations of unconstitutionality relate to educational financing statutes enacted subsequent to the 1979 establishment of the GTB program which the court concluded had impermissibly undermined the capacity of that program to diminish continued disparities in educational expenditures. The court pointed to a variety of statutory enactments that served to perpetuate undesirable disparities. State funding has been phased in at a lower level and a slower rate than originally contemplated, so that for 1984-1985, funding has been provided at a 95 percent rather than a 100 percent level, and full funding postponed to a seventh year.20 Towns have been permitted to delay in moving to full MER contributions.21 The legislature has also amended the program to substitute three year old data for two year old data in the calculation of the relevant grants.22 The court determined that, although access to educational opportunities had been improved by the additional state and local educational funds generated by the GTB program, the [44] post-1979 amendments resulted in continued financial disparities which, in the absence of a compelling state interest, unconstitutionally interfered with the plaintiffs’ fundamental constitutional rights.
Relying on statistical evidence of continued significant disparities in local educational expenditures,23 the court declared that the gap between the educational resources of the property-rich towns and the property-poor towns must be narrowed by elimination of: (1) minimum aid grants, General Statutes § 10-262c (f) as amended by Public Acts, Spec. Sess., June, 1983, No. 4; (2) deferral of full GTB financing, General Statutes § 10-262c (c) as amended by Public Acts, Spec. Sess., June, 1983, No. 4; (3) alternate MER requirements, General Statutes § 10-262e (d) as amended by Public Acts 1983, No. 83-363, and Public Acts, Spec. Sess., June, 1983, No. 4; and (4) three year old data in the calculation of GTB grants, General Statutes § 10-261 (a) as amended by Public Acts 1983, No. 83-363, and Public Acts, Spec. Sess., June, 1983, No. 4. Accordingly, the court ordered, by way of remedy, that various designated governmental officials disburse or collect funds in order to implement the court’s conclusions of unconstitutionality.24
We agree with the trial court that the plaintiffs established a factual foundation for the court’s conclusion that continued disparities in educational financing required strict scrutiny of the state statutes that have an impact on educational equity. We disagree, however, with the substantive standard by which the trial court tested the validity of the statutes and with the procedural failure of the trial court to afford all the interested parties an opportunity to be heard on the remedial implications of the court’s decisions on unconstitutionality.
[45] It is clear from the trial court’s memorandum of decision that the court found the statutes before it to be unconstitutional because the defendants had failed to prove that the statutes met a compelling state interest. As we have already indicated in this opinion, we believe that the proper test requires the state to prove that the amendments reasonably advanced a rational state policy and that they did not result in an unconstitutionally large disparity.25 For this reason, we must remand this case, as to the amendments only, for further proceedings in the trial court in accordance with the substantive standard which we have now articulated.
It is also clear that the trial court’s judgment is procedurally flawed. Just as our decision in Horton I set the substantive parameters for assessment of the constitutionality of the present plan for state financing of public secondary school education, so our decision in Horton v. Meskill, 187 Conn. 187, 445 A.2d 579 (1982) (Horton II) set the procedural stage. There we discussed the role of the various municipalities who have an obvious interest in the outcome of this litigation. We noted first that “the rights at stake are the students’ constitutional rights to equal protection and free public education. . . . The state’s duty to provide [46] education is owed to the students, not the municipalities.” (Emphasis in original.) Id., 195. We referred also to our established case law that generally forbids municipalities, because they are creations of the state, from challenging the constitutionality of the state’s laws. Id., 196. We concluded that the interests of the municipalities could reasonably be protected by having a bifurcated trial. Although the municipalities were precluded “from participating on either side in the court’s consideration of the constitutionality of the present legislative financing system,” they could play a role in proceedings “to aid the court in determining appropriate relief in the event the legislative financing system is found to be unconstitutional.” Id., 198. Guided by this holding, the trial court agreed to hold a bifurcated hearing with respect to all the interested parties. The court stated that it would first determine whether the current legislation was constitutional. Thereafter, in the event that the legislation were found to be unconstitutional, it would determine, after a separate remedial hearing, what relief should be ordered to remedy the situation.
In light of this commitment to full participation by all of the parties in the remedial judgments that would ensue if the statutes at issue were found to be constitutionally defective, further trial court consideration of all aspects of their validity is desirable. Our decision in Horton I gave to the trial court, and to the litigants at trial, only limited guidance about the precise constitutional test by which to measure access to substantially equal educational opportunities. It may well be that additional hearings will help to sharpen the difficult substantive judgments that will have to be made. In litigation that raises constitutional issues that have systemic implications for the operation of government, it is appropriate for a trial court to pursue a joint consideration of right and remedy. See Gaines v. Manson, [47] 194 Conn. 510, 519-20, 481 A.2d 1084 (1984). Postponement of final adjudication on the merits is particularly appropriate when the relief that the plaintiffs seek is a mandatory or a negative injunction. As in cases in which courts are asked to fashion an equitable remedy for racial discrimination in education, where fundamental rights are similarly at issue, equitable principles require a balance of three factors: the nature and the scope of the constitutional violation, the plaintiffs right to meaningful relief, and the interests of state and local authorities in managing their own affairs. Milliken v. Bradley, 433 U.S. 267, 279-81, 97 S. Ct. 2749, 53 L. Ed. 2d 745 (1977). Our own cases have similarly acknowledged that a court, in the exercise of its discretion to frame injunctive relief, must “balance the competing interests of the parties” to assure that the relief it grants is “ ‘compatible with the equities of the case’ Dukes v. Durante, 192 Conn. 207, 225, 471 A.2d 1368 (1984); and takes account of the possibility of “embarrassment to the operations of government.” CEUI v. CSEA, 183 Conn. 235, 248-49, 439 A.2d 321 (1981). Remand is therefore required to determine whether the challenged statutes are unconstitutional and to frame whatever orders for equitable relief may be appropriate.
There is error on the appeals; the judgments of the trial court are set aside and the cases are remanded for further proceedings in accordance with this opinion; there is no error on the cross appeals.
In this opinion the other judges concurred.