Chancellor Carmen Fariña asked, and principals delivered.

Specifically, they submitted about 800 of their rooms for consideration as new pre-kindergarten classrooms—space the city needs in order to carry out its ambitious pre-K expansion. The exact figures will be announced at a press conference Tuesday, Fariña told parents at a Far Rockaway town hall meeting on Monday night.

She and Mayor Bill de Blasio are set to make an announcement at 12:15 p.m. at P.S. 130 in Manhattan. De Blasio’s schedule notes he will tour a pre-K classroom after the event.

“We sent an SOS to principals,” Fariña said. “I simply asked principals, how many of you have seats and let us know where they are.”

(Later in the event, Fariña contradicted herself to say that 800 principals offered rooms, though that is an unlikely figure given that the city has 1,700 or so schools.)

The city’s pre-K implementation plan says 2,000 new pre-K classrooms will be needed across the city, and about 4,000 had been identified as potentially available in city school buildings. But the 4,000 figure comes from principal space surveys from the 2012-13 school year, and says nothing about how many pre-K classrooms schools are willing to accommodate.

Since a sizable chunk of the necessary 2,000 new classrooms are likely to come from community based organizations, the city may not need to look beyond the 800 volunteered classrooms for Department of Education space.

That would be an important signal that schools are willing partners in the city’s pre-K push, even when it involves space-sharing, and a far cry from the co-location fights of Bloomberg era that Fariña’s department was trying to contrast its decision-making with on Monday.

Identifying potential classrooms is just step one, though. “The reality is, now what we have to do is find out how many of the sites that have been designated meet our requirements,” Fariña said.