The fight between charter schools and the de Blasio administration is heating up, with charter schools accusing the city of standing in the way of their getting more classroom space. Our education reporter, Lindsey Christ, has more.

At Boys Prep Bronx Charter School, the principal's office is a converted broom closet.

It's one of 50 charter schools that says, over the next two years, they won't have room for all their students.  

According to the leaders of the city's largest charter school networks, Mayor de Blasio's administration is delaying the approval process.

"Things are going slower than we had hoped," said CEO of Public Prep, Ian Rowe. "And it's December. And parents want to know where their kids are going to school, potential teachers want to know where they're going to be working and so we are very anxious."

In a letter obtained by NY1, leaders of six charter networks serving 45,000 students, told the Mayor that working with his team is onerous. They urge him to finalize decisions on where charter schools will be sited, saying hundreds of families don't know where their kids will attend school next year.

"The biggest consequence of a delay is that a parent desperately wants to send their son or daughter to a great school doesn't have that option," said Rowe.

De Blasio has not been a big fan of charter schools. Nearly three years ago, the charters fought him over whether they were entitled to space in public school buildings. The charters triumphed, with a new state law requiring the city to provide school space or pay for private space. 

Now the charter leaders accuse the city of sabotaging the process by appealing decisions and delaying whenever possible.

The campaign is once again very public, with television ads:

"Even though the Mayor has over 200 half empty school buildings, he is shutting them out."

And City Hall rallies: 

"The only explanation for why we are holding get another press conference is that the Mayor is playing politics," said Success Academy CEO Eva Moskowitz.

The City says it continues to work with the charters, with proposals for seven schools finalized and four more in the works.

Regarding Boys Prep, the State Education Commissioner says the city needs to pay for space — and the city is now appealing the decision in court.