On the question of accountability, the Referees concluded that existing state systems, identifying schools that perform poorly and sanctioning failing schools, already provide adequate accountability, and that no new Office of Educational Accountability should be created. They recommended, however, that the current system should be enhanced by the development of a comprehensive "sound basic education" plan by the New York City Department of Education. Supreme Court confirmed the Judicial Referees' Report and Recommendations. The Appellate Division vacated that confirmation (29 AD3d 175 [2006]). It found support in the record for the State's "cost-effectiveness" approach, as well as for its weighting for economically disadvantaged students. Noting that record support, the Appellate Division observed that "Supreme Court should not have substituted the Referees' opinion for that of the State . . . [and] converted a factor that was arguable and reasonable for the Legislature and Governor to consider into an incontrovertible fact. As long as the State's choices remained within the range of professionally accepted practices in determining the costs of a sound basic education, Supreme Court should have left the conclusions for legislative and gubernatorial consideration and determination." (29 AD3d at 184.) Citing Governor Pataki's proposal to increase funding of the New York City School District by $4.7 billion (over a period of five years), the Appellate Division directed the Governor and Legislature to appropriate at least $4.7 billion in additional operating funds (phased in over four years).[FN4] The Appellate Division also directed the Governor and Legislature to "implement a capital improvement plan that expends $9.179 billion{**8 NY3d at 27} over the next five years or otherwise satisfies the city schools' constitutionally recognized capital needs" (29 AD3d at 191). Plaintiffs CFE et al. appeal pursuant to CPLR 5601 (a) and (b) (1). The state defendants crossappeal under CPLR 5601 (b) (1). II. [*8] The Judicial Referees' Report, dated November 30, 2004, commands our attention as well as our respect; it is likely that much of value may be learned from the Referees' careful consideration of methods of ascertaining the cost of a sound basic education and reforms to the current system of public school financing. Nevertheless, we hold that Supreme Court erred by, in effect, commissioning a de novo review of the compliance question. The role of the courts is not, as Supreme Court assumed, to determine the best way to calculate the cost of a sound basic education in New York City schools, but to determine whether the State's proposed calculation of that cost is rational. Supreme Court should not have endorsed an examination in which the cost of a sound basic education in New York was calculated anew, when the state budget plan had already reasonably calculated that cost. In this respect, we agree with the Appellate Division. It was error to confirm the Referees' Report. We differ from the Appellate Division, however, in two respects. First, we observe that the state