More than 6,300 overcrowded classrooms were enough to prompt a press conference by the teachers union last September decrying the city’s inattention to class sizes. This year, 6,447 overcrowded classrooms weren’t.

In a shift indicative of the new working relationship between city government and the United Federation of Teachers, the number of overcrowded classes was noted only in an article in the union’s internal newspaper, New York Teacher. And rather than report overcrowded classes at their peak, the story says 3,500 classes exceeded limits — a number from after the city had already begun to reduce overcrowding.

The numbers come from class counts done by teachers during a two-week period at the start of every school year. When the class sizes exceed the limit agreed to in the union’s contract, the union can file grievances to get classes reduced in size. In high school grades, for instance, the contract says class sizes can’t exceed 34 students. (The UFT provided this year’s peak figure in response to requests from Chalkbeat.)

For years, class sizes stayed flat or decreased during the Bloomberg years. But they began to increase in 2009, especially in elementary grades, following budget cuts caused by the economic recession. That trend has continued over the last five years, with early grades reaching a 14-year high in 2013, according to the UFT.

The average first-grade class, for instance, had 24 students last year, up from 22 in 2010, according to a city report released earlier this month. Citywide, average class sizes are still below the contract’s limits.

Class sizes are intensely debated in New York City, where school overcrowding is a top concern among both parents and teachers. Former Mayor Michael Bloomberg was dismissive of growing class sizes, often saying that he’d prefer to have great teachers serving more students than smaller classes with inferior teachers.

As a candidate for mayor, Bill de Blasio said he would establish class size reduction goals that would be achieved by the end of his first term. In a speech to principals in January, Chancellor Carmen Fariña said reducing class sizes were a priority, but more of a long-term goal.

Since taking office, de Blasio has targeted new school construction toward perennially overcrowded areas. And education department officials also said that a space-sharing working group, whose recommendations are expected to be released this fall, will also be working on reducing class sizes.

But advocates say that, so far, the new administration’s efforts have not amounted to a serious plan. On Sept. 22, a group of 73 university professors signed a letter urging de Blasio to implement a plan to reduce class sizes, arguing the reductions would especially help at-risk students and that large classes in older grades could undermine the benefits of his efforts to expand pre-kindergarten.

“There’s no evidence that I see that either the city or the UFT has this on their agenda as an issue that needs to be addressed,” Class Size Matters Executive Director Leonie Haimson said.

Before de Blasio was elected, the UFT went to great lengths to slam the city when it released class size reports at September press conferences and rallies in recent years. To maximize the impact of their analysis, the union calculated the total number of overcrowded classes by adding up the most-crowded days, even if numbers decreased throughout during the survey period.

In addition to the union’s reports, the city issues its own class size tallies each November, after schools set their official registers for the year, often confirming trends noted by the union.

Haimson said the contractual violations, while important to address, were only “the tip of the iceberg.” She said the city should use funds to lower class sizes so that they are more in line with goals set forth in the 2007 Campaign for Fiscal Equity lawsuit settlement, which required the state to earmark money specifically for six different purposes, including reducing class size.

Privately, the union is still taking action. Earlier this month, the United Federation of Teachers filed demands for arbitration for oversized classes at 537 schools where the overcrowding is concentrated. Three Queens high schools—Hillcrest, Forest Hills, and Benjamin Cardozo—alone housed 605 of the oversized classes, according to New York Teacher.

UFT Michael Mulgrew told the union publication that he was optimistic that the new administration was open to lowering class sizes quickly.