It's a nasty New York City real estate fight, with both sides accusing the other of damaging, even dooming, schoolchildren.

On Thursday, dozens of parents stood with charter school leader Eva Moskowitz outside City Hall, demanding more space for her Success Academy charter schools -- and bashing Mayor Bill de Blasio. 

"He actually got elected by both charter parents and district," Moskowitz said. "He represents all the parents, but unfortunately he has decided, once again, to discriminate against charter parents."

The city is supposed the give the taxpayer-funded but privately managed charters space in public school buildings when it's available. The de Blasio administration says it has been generous with allocating space. Success Academy officials vehemently disagree.

"He's a landlord," Moskowitz said. "He's sitting on top of empty space and not giving it to kids and families and to an organization that has a stellar track record of educating kids."

The Manhattan Institute, a conservative think tank, said last spring that 192 city school buildings have space for 300 more students. The city says it has provided space for 5,000 Success Academy students since 2014 and that it already has plans for much of the available space cited by the Manhattan Institute. 

Success rallies like this have been a regular occurrence at City Hall, especially under de Blasio. The mayor has long said his priority is the traditional public school system. He suggests that some charters nudge out struggling students, who then must be accepted by regular public schools.

Still, the charters keep growing, becoming an increasingly potent lobbying force.

Success Academy has at least one Democratic state lawmaker on its side: Bronx Assemblyman Marcos Crespo. He recently enrolled two of his children in a Success school and had a lead role at the rally.

"Take the politics out of it," Crespo said. "You're about results. Look at the data. The data shows this school is working. Don't deny them their growth."

Seventeen thousand students attend the 47 Success charter schools in the city. The network hopes to grow to 100 schools in six years - if they can find the space.