repairs in each of the 921 structures. The actual calculation of this per square foot cost, and the person who performed the calculation, were not described by Mr. O'Toole or by any of defendants' other witnesses. Apparently, the figure was arrived at by dividing a school building's square footage by BCAS cost estimates. While this calculation would appear to be a plausible method for deriving a per square foot repair cost, it did not receive the imprimatur of Mr. O'Toole or any other expert at trial. Relying on BCAS, Mr. O'Toole opined that per square foot costs of $100 or less indicated a building that was in "fair" condition. Eighty-nine percent of the buildings in his survey by this measure were in fair condition. Mr. O'Toole concluded that these two analyses reinforce each other in supporting his ultimate conclusion that the vast majority of New York City public school buildings are in fair condition, requiring at most only preventive maintenance. Mr. O'Toole's analyses are not persuasive. Crucially, Mr. O'Toole's first analysis made no distinction among the 251 components measured. It made no attempt to weigh each component's centrality to a school's functioning and does not attempt to account for BCAS' "purpose of action" and "urgency of action" ratings. It did not reveal which 41 components had an average less than three. An analysis based on the averages of components, standing alone, is of no probative value. Numerous schools have at least some components that score below the average. Depending on the components in question, a school with a handful of components below "fair" may have a severely compromised infrastructure. The crucial analysis, which was presented by plaintiffs, is what BCAS reveals about individual schools, not about individual components. [187 [187 Misc.2d Misc.2d 45] 45] With respect to Mr. O'Toole's second analysis, plaintiffs point out that his cost per square foot exercise is based upon only 921 of the approximately 1,400 structures included in BCAS. Mr. O'Toole testified that he collected these 921 structures by cross-referencing BOE and SED files regarding cost and square footage, respectively, and that the failure to match all the buildings in the BCAS survey was a function of the incongruence of the two files, not of any selection on his part. From this he concluded that his sample of school buildings was random. Plaintiffs offered no evidence to rebut this conclusion. Nonetheless, the incompleteness of Mr. O'Toole's survey does cast some doubt on his analysis. There was no testimony that gaps in discovery create a random sample. It is at least plausible that the lack of congruence between BOE and SED files may have been caused by some factor that was not random. Another weakness of this analysis was that the actual calculation of the repair cost per square foot for each building was not set forth explicitly by defendants. Finally, Mr. O'Toole's "cost per square foot" analysis was compromised by his reliance on cost estimates included in the BCAS, rather than on more accurate refinements to those cost estimates later generated by BOE for inclusion in its 2000-2004 five-year plan. d. Old Buildings and Changing Needs In addition to the major structural deficiencies described above, New York City public school buildings contain antiquated science laboratories and wiring, heating, and air conditioning systems. In large measure this is a function of the buildings' age. Most City school buildings were built in an era when there was no need for computers, summer school, or more than rudimentary laboratory equipment. More than half of the buildings in the system are more than 58 years old. Science labs are often obsolete or absent altogether in City public schools. According to BOE figures a minimum of 31 high schools lack a science lab of any description, leaving over 16,000 high school students without access to this crucial resource. In schools that do have labs, a single lab must be used for biology, chemistry and physics classes. Each subject area involves different equipment, and the near-constant use of labs in schools can restrict the complexity of experiments performed in the lab. Inadequate wiring can impede a school's ability to offer computer education and other initiatives. Computers also require air conditioning to work properly during the warmer months. [187 [187 Misc.2d Misc.2d 46] 46] The lack of air conditioning can also take its toll on teachers and students during the summer session recently inaugurated by BOE. Only 7,344 out of approximately 35,000 classrooms in the system have air conditioning. In addition, there was credible evidence that existing air conditioning units often do not function properly. The evidence demonstrates that New York City's public schools have a substantial backlog of interior repairs. New York City's schools are plagued by the disrepair of such basic amenities as lights, toilets, plaster and paint. Finally, as discussed in subsection G below, overcrowding in the City's public schools is both a cause of facilities' deterioration and an impediment to remedial measures. Overcrowding has necessitated the use of important resources such as libraries, music and art rooms, and gymnasiums as classrooms. Overcrowding makes it difficult to conduct proper repairs without severe displacement of students. 2 . T h e C a u s a l L i n k B e t w e e n I n a d e q u at e S c h o o l F a c i l i t i e s a n d S t u d e n t O u t c o m e s Plaintiffs argue that there is no need to inquire into the causal link between inadequate school facilities and student outcomes, arguing that minimally adequate school facilities are an entitlement under the Court of Appeals 1995 decision. This court disagrees. The Court of Appeals 1995 decision states that the adequacy of school facilities is to be measured by whether they "permit children to learn." (Campaign for Fiscal Equity v State of New York, 86 N.Y.2d 307, 317, supra.) Accordingly, this court must examine the effect of poor physical conditions on students' ability to learn. The State Legislature, SED and BOE have all concluded that the City's decaying and decrepit school facilities impede learning but have not attempted to quantify the negative effect of crumbling school buildings on student performance. Plaintiffs presented numerous SED and BOE witnesses who testified that the physical plant of a school can have a marked effect upon learning. In the case of absent or obsolete science labs the connection is obvious. Students cannot learn a subject without the requisite tools to do so. Similarly,