The city is so desperate to find housing for its flood of migrants that it is now using school buildings — with “several families” already secretly moved into a Brooklyn elementary-school gym, The Post has learned.

The principal at PS 188 on Coney Island alerted parents in a letter Friday that the school had been chosen as one of the “emergency, temporary sites to house individuals and families who are seeking asylum” in the Big Apple.

Starting Thursday night, “several families will be utilizing the stand-alone gym at your school on a short-term basis,” Principal Leslie King wrote.

More families are expected to be sent to the gym in the next few days, too, a local pol said.

The Michael E. Berdy School of the Arts on Neptune Avenue got its hard-earned $10.3 million gym more than a decade ago.

It was not clear Friday what the school’s pupils will do without their gym while the migrants live there.

But King tried to assure the students and their parents that the situation “should not impact school operations, nor will the families have access to any other part of the school where students and staff are.

“Our number one priority is ensuring the safety of our students and our community,” she wrote, vowing to “dedicate the necessary resources to back up that commitment.”

Local city Councilman Ari Kagan told The Post on Friday that the elementary school is “totally the wrong place” to house migrants.

“It’s a school gym — it’s not a hotel, it’s not a shelter!” said the Republican, who last year ditched the Democrats for being too soft on crime.

He said the school did not have showers or other basic facilities for the migrants.

Kagan added that insiders at City Hall have admitted to him they are jittery at what public reaction will be to the move.

“They told me this: They are preparing for the worst,” he said.

“This is why they didn’t notify people because they knew the community would be against it,” Kagan said.

He said officials told him to “expect in the next two days even more” families “because of the expiration of Article 42,” the pandemic-era law that allowed the US to boot many migrants at the border during the pandemic.

“Coney Island and New York City should not be responsible for the failed policies of the Biden administration,” Kagan said. “I really hope it’s not a permanent shelter.

“We cannot have 24-7 police presence here,” he later added in a video on Twitter, referring to cops posted at the school to monitor the migrant situation and demanding open communication about the controversial plans. “Everyone should feel safe in this beautiful community.”

City Councilman Justin Brannan tweeted that he only found out about the makeshift shelter “after being alerted by concerned community members.”

He said he was then told that “the city is staging the gymnasium building to house children with families.

“Yes, this is a crisis, and we need to move fast and be flexible in accommodating asylum seekers,” he said.

But “housing families in an active public school gymnasium is not the solution.”

LittleAfrica News, which first revealed the gym plan, said 64 cots had already been set up, with the plan to eventually house up to to 100 migrants.

City Hall did not respond to The Post’s requests for comment.

The move comes as City Hall officials are still scrambling to house the massive influx of migrants that is expected to only mushroom now that Title 42 has been lifted.

The situation is so dire, officials have looked at major landmarks such as the Flatiron Building and JFK International Airport, as well as the city’s most beloved parks — Manhattan’s Central Park, Brooklyn’s Prospect Park, and the Flushing Meadows Corona Park in Queens.

As of this week, at least 65,000 asylum-seekers have gone through the Big Apple’s system and been offered a place to rest at night since last spring. More than 39,400 are currently being cared for.

On Wednesday, Mayor Eric Adams signed an executive order that temporarily eases housing requirements involving homeless families seeking shelter, including the right for a bed, during the crisis.

“This is not a decision taken lightly, and we will make every effort to get asylum-seekers into the shelter as quickly as possible as we have done since Day One,” City Hall spokesperson Fabian Levy said at the time.

Early Friday, Public Advocate Jumaane Williams greeted another two busloads of migrants arriving at Manhattan’s Port Authority, carrying around 200 new arrivals.