New York City’s charter school battle lines are as clear as ever. Last week, the mayor fired the latest shot by dismissing some charter schools’ test score gains as a product of test prep rather than “actually teaching kids.”

Charter school advocates, who called his comments “insulting” and “mean-spirited,” took to the op-ed page and are planning another massive rally this September to call on the city to “stand with public charter schools”

But while the debate rages on, the city’s power to stop the charter sector from expanding has slowly waned. The Department of Education can no longer authorize new schools, the state doubled the city’s charter school cap, and legislation requires the city to provide rent money for charter schools using private space.

That leaves little practical recourse for de Blasio to hamper charter schools, some argue, regardless of how he feels about them.

“It seems completely like rhetoric to me,” said Dirk Tillotson, the founder and executive director of the nonprofit Great School Choices, which helps launch community-based charter schools. “I don’t think the education department has any credibility, and he particularly doesn’t have any credibility on charters.”

Others say that rhetoric itself has power, and that the mayor can complicate the process for charter schools trying to find public space. Here’s a look at what the city can — and can’t — do when it comes to charter schools.

Can the mayor stop charter schools from expanding? (No, that’s not him.)

The city’s Department of Education used to be able to approve or “authorize” charters, but it lost that power in a series of state legislative changes passed during the Race to the Top era. Now, charter approval and oversight is left to the New York State Board of Regents and SUNY.

Roughly 50 charter schools still remain under the control of the Department of Education, holdovers from when the city used to authorize charters. In February, the city moved to close three low-performing charter schools under its control. Even the New York City Charter School Center did not protest those closures.

“Nobody wants to see a school closed, but it’s important that authorizers maintain high standards and hold charters accountable,” said James Merriman, CEO of the Charter School Center, at the time.

Charter schools currently serve 95,000 students, roughly 8.6 percent of the student population, and a state cap controls their growth. Last year the state doubled limit on the number of new charter schools that can start in New York City from 25 to 50.

Can he deny charter schools space? (Not technically, but advocates argue he can make it difficult.)

School space has been a key flash point between de Blasio and advocates.

Success Academy CEO Eva Moskowitz led the charge against de Blasio in 2014 with a crusade to secure charter school space — and it’s a battle she won. The state passed a law requiring the city to provide new charter schools with space inside city buildings or fund private rent for schools.

Despite that law, some charter advocates argue de Blasio could do a better job finding public space for charter schools. Public space is often preferable to private space, they say, since those buildings are already designed to accommodate students.

In June, the pro-charter group Families for Excellent Schools released a report claiming there are 67 schools in the city with more than 500 seats available for students. City officials called that claim “misleading,” since many factors determine whether a given space is appropriate for a school, including projected enrollment and the type of seats available.

Still, leaders of the city’s largest charter school networks said the city could provide more space to schools with fewer strings attached.

“The process was often marred by unnecessary hurdles, difficulties and delays,” wrote a group of charter school leaders in an open letter to de Blasio. “Sadly, in other cases, public charter schools were not provided with public facilities, leaving thousands of families stranded without a high-­quality option or building.”

Can he control charters’ ability to provide pre-K? (Not exactly)

This fall, Success Academy CEO Eva Moskowitz refused to sign the city’s pre-K contract, arguing that being asked to do so is illegal since Success is overseen by SUNY, not the Department of Education.

“One of the primary reasons Success scholars and teachers have been able to achieve so much is their ability to learn and work without the shackles of bureaucracy exemplified by this 241-page contract,” said Success spokesman Stefan Friedman in February.

City officials fired back, insisting that they have a responsibility to ensure pre-K standards remain high in every school, including charter schools. Moskowitz appealed to State Commissioner MaryEllen Elia, who denied her request. In response, she cancelled her pre-K classes this year.

State Senate Majority Leader John Flanagan appeared to throw his weight behind Moskowitz when he sent a letter to Governor Andrew Cuomo, arguing that the state should help ease the regulatory burdens on charter schools. It is still unclear how the law will be interpreted, but Assembly Speaker Heastie sent a dueling letter to the governor, disagreeing with Flanagan’s interpretation.

Does the rhetoric itself have power? (Possibly, but only if people listen)

Even if he has little practical power over charter schools, some say his words themselves are deflating.

“I think it does hurt charter schools when he casts aspersions and basically says their hard work to help [students] meet Common Core standards is really just a glorified parlor trick,” Merriman said.

Some, like Tillotson, are skeptical that the mayor has enough allies to make a dent at the state level. “He can politically lobby, but he’s got no political juice,” Tillotson said.

But others, like Bob Bellafiore, an education consultant who works with some charter schools, say the mayor’s words matter.

“What he does have is the bully pulpit. He’s the mayor, he has significant following in the city,” Bellafiore said. “He has a bullhorn and that has an impact.”