NEW YORK — More than 73% of New York City’s public school classrooms now adhere to the state’s class size law, after New York City Mayor Zohran Mamdani pushed to delay the mandate that would have required greater compliance this school year, according to new data released Friday.

The 2022 state law requires the phasing in of limits between 20 and 25 students per class, depending on grade level.

Gov. Kathy Hochul and the state Legislature agreed last session to give Mamdani two more years to implement the caps, delaying full compliance until September 2030 with intermediate deadlines along the way. As a result of the changes, this year’s mandated rate declined from 80% to 70%, with public schools surpassing the revised target.

But in order to hit that target, education officials quietly updated the way they report class size data, including the addition of specialty subjects and exam prep courses. The city Department of Education also lost hundreds of teachers, raising questions about if the progress should be attributed to active efforts to lower class sizes — or if fewer students enrolled in the public schools.

Still, the Mamdani administration claimed victory in a news release.

“The days of overcrowded classrooms and students struggling to get the attention of their teachers are coming to an end,” Mamdani said.

As of this fall, the number of schools that have achieved full compliance with the law more than doubled, for a total of 254 schools where all classrooms meet the size caps, education officials said.

Other schools are getting closer. More than 640 schools have reached at least 90% compliance, according to the report. Meanwhile, the number of schools where half of classrooms exceed the caps has fallen by more than 230.

Class size compliance increased across all grade bands, with the largest gains in middle school: 7.2 percentage points, the data showed.

Education officials touted the improved compliance without exempting classes from the calculation, including the city’s specialized high schools, which have long been excused from lowering class sizes. Last year, roughly 10,500 classrooms were exempt for a lack of space, staffing shortages or other reasons, according to an analysis by the education nonprofit news source Chalkbeat New York.

But behind the scenes, the Department of Education revised the compliance rate to add new classes — which had not been included in previous compliance reporting — including daily arts, science and physical education subjects known as “cluster classes” in elementary schools, plus exam preparation courses in middle and high schools.

“Those aren’t regular academic classes,” Leonie Haimson, executive director of the advocacy group Class Size Matters, said of the exam prep classes. “That makes no sense to me.”

The Department of Education pushed back against the concern. Education officials estimated that without updates to its reporting mechanisms, the public schools would have fallen just short of the required 70% compliance but been able to use the specialized high school exemptions to adhere to the law.

“I don’t know that I would call it a changing methodology,” Erin Gehant, a senior adviser to Chancellor Kamar Samuels’ top deputy, said in an interview with The New York Daily News. “The classes that we added are classes that children sit in every single day.”

“We’re continually updating our reports with new data, and continuing to refine our approach each year.”

Further complicating the analysis is a declining teacher headcount.

The total number of classroom teachers fell by 439 positions this school year to 69,434 — though the number remains thousands of teachers above what it was when the smaller class size push started, according to the data.

It was not immediately clear as of Friday how the Department of Education was able to increase compliance with the class size law while losing teachers. Student enrollment data are set to be released early next week, which could help explain the discrepancy.

City Hall has said the class size law compliance extension will save $500 million as Mamdani needed to close a multibillion-dollar budget gap, though it was unclear whether those savings remained intact after the mayor added $244 million for teacher hiring across more than 360 schools. The Mamdani administration also added $1.5 billion to create more physical classroom space, part of a total of $7.6 billion in capital funding for smaller class sizes.

The Department of Education also plans to spend a to-be-determined amount on principal bonuses for the additional work required to lower class sizes, The Daily News first reported in September. Similar bonuses for teachers working in exempt classrooms are largely moot, given the city’s lack of reliance on exemptions, education officials confirmed.

Schools with the highest percentages of Black and Hispanic students have 84% and 86% of classes at or below the caps, compared to those with Asian and white students, which reported 63% and 60%, respectively.

Some of the highest compliance rates are in neighborhoods such as Bedford-Stuyvesant and Bushwick, where families are being priced out and young professionals are moving in, while districts that include Brooklyn Heights, Forest Hills and other areas of Queens are among the lowest.

“I know from my days as a teacher and a school leader that students learn best when instruction is tailored to their unique strengths, needs and goals,” Samuels said in a statement. “Smaller class sizes help make that a reality.”

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