In September 2022, New York enacted legislation requiring New York City public schools to reduce class sizes across all grade levels. The law set a schedule of intermediate compliance benchmarks to ensure that by the start of the 2027–28 school year, no New York City public school class exceeded 25 students. To accomplish this goal, New York City has already invested $640 million, with an estimated $949 million to $1.7 billion more needed to reach full compliance.

Now two years into its five-year implementation schedule, we assess class size compliance rates by school level, geography, student need, and student achievement. We also assess how funding was distributed across schools in fiscal year 2026.

Why This Matters

Causal evidence on the effects of class size reduction is limited, with most studies finding negligible effects. The research that does show positive benefits for student achievement is strongest at the elementary school level, while evidence remains inconclusive at the middle and high school levels.

Because New York City has nearly four times as many high school classes as it does elementary school classes and more than twice as many high school classes as middle school classes, the road to full compliance must go through high schools. This means that successful implementation of New York’s class size reduction law—and the substantial investment of public dollars it requires—relies on changes with the thinnest empirical evidence.

What We Found

Overall, class size compliance stands at 64 percent across all New York City public schools, but there is substantial variation by borough, economic need, and student achievement:

• The Bronx leads among the city’s five boroughs with 70.9 percent compliance, while Staten Island (50.2 percent) has the lowest compliance rate.
• Schools serving students with the greatest economic need show higher compliance than those with less need (77.7 percent and 52.2 percent).
• Schools with the lowest compliance rates have substantially higher student achievement, while schools meeting size caps have lower average test

These findings largely align with pre-implementation patterns and, as such, create a perverse funding incentive. Because the schools serving already high-achieving students are farthest from compliance goals, they will receive more funding simply because they have maintained larger class sizes historically. Meanwhile, the schools serving struggling students—whom research suggest would benefit from smaller class sizes—have already achieved higher compliance rates and will receive fewer resources.

Achieving compliance will require investment in additional teachers and physical classroom space. We model the number of teachers New York City public schools would need to hire given current classroom space constraints, finding that at 100 percent compliance, almost 17,000 addition teachers would be needed, adding more than $1.83 billion in annual salaries.

As New York City continues implementation of its multiyear, multimillion-dollar effort to reduce class sizes, this research raises the question of whether the goal of this law should be to meet a simple counting standard or to maximize student achievement per dollar spent. Rigorous evaluation, particularly at the middle and high school level, will be needed to determine whether this historic investment delivers commensurate benefits.