Critics have long said that the city is using the wrong metrics to decide how much space schools actually have to serve students. On Tuesday, the Department of Education announced it will make revisions to the Blue Book, a 475-page document released annually that inventories how much space schools do — or don't — have.

The problem with the Blue Book is that it didn't take into account building design or the needs of the students. For example, until last year, it counted trailers as part of a school's capacity, even though trailers are supposed to be temporary. And it didn't account for common space, like gyms or cafeterias.

Inaccurate reporting has meant that the city hasn't gotten a full picture of how squeezed the schools are. 

Mayor Bill de Blasio's administration had convened a working group to examine the Blue Book, and six months ago, they submitted recommendations to the mayor and Schools Chancellor Carmen Fariña. 

"They certainly were aware that the Blue Book numbers were flawed," said Shino Tanikawa, president of the Community Education Council for District 2 and a co-chair of the Blue Book working group. "The debate was over how to fix it and how far to go."

Of the 13 recommendations submitted to the city, the Department of Education will adopt seven. Key among them is recognizing the need for schools to designate and account for private counseling space in elementary and middle schools, and allocating a minimum of two cluster rooms — spaces for subjects like art or technology — to even small elementary schools with a student population under 250. 

Other recommendations adopted by the city have to do with gathering better data from principals on the common spaces they have and how many students with disabilities or English Language Learners are at each school.

However, the city did not adopt a recommendation to align Blue Book calculations to the smaller class sizes required by the Contracts for Excellence law passed in 2007. 

As a candidate for mayor, de Blasio had said that he would prioritize reducing class sizes, and would comply with the Contracts for Excellence class size targets. Advocates on the working group pushed hard for this change, contending that the Blue Book must reflect these goals in order to document how many classroom seats the city truly needs.

"Certainly for me and for many of us, the class size issue was the biggest issue that we felt would have the greatest impact on bringing us to painting an accurate picture of reality and making sure that all kids got access to an adequate education — hands down," said Lisa Donlan, president of the Community Education Council for District 1 and a member of the working group.

City education officials said reducing class size was still a shared goal.