New York City Mayor Bill de Blasio is forging ahead with his plan to provide free, universal and full-day prekindergarten. When he’s not fending off the attentions of Gov. Andrew Cuomo, who has his own plan for getting pre-K done, de Blasio has faced another challenge: Finding enough space to house the estimated 54,000 students meant to start pre-K in September.

There has been talk about turning to charter schools, which some observers found a little funny considering that de Blasio has decried their supposed destructive effect on the educational system. And while the mayor has said that he’ll indeed make use of existing schools as well as possible, his Ready to Launch plan released on Monday floats an additional option: Mapping and tapping the city’s already-paid-for but underused public spaces.

After converting part-time seats to full-day seats and otherwise expanding programs already in place, the city will need some 2,000 more classrooms with seats for 12,000 students. A Department of Education survey of available space is slated to wrap up by the end of next month, but de Blasio has indicated that the city will also look at “space in branches of the New York Public Library.” According to the news site DNAinfo, the mayor’s office says that it has looked at spaces in New York City Housing Authority buildings, too.

Whether or not those spaces are equipped for thousands of the littlest New Yorkers running around all day, the raw material is there. NYCHA runs more than 330 housing developments in the city. The New York Public Library operates nearly 90 branches, sprinkled all over Manhattan, Staten Island and the Bronx. While de Blasio — in a horrible affront to his fellow outer-borough residents — didn’t mention the Queens Public Library or the Brooklyn Public Library, each has another 60 or so branches.

Nancy Scola is a Washington, DC-based journalist whose work tends to focus on the intersections of technology, politics, and public policy. Shortly after returning from Havana she started as a tech reporter at POLITICO.