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The city teachers union vowed Sunday to file a complaint with the state Labor Department claiming that Big Apple schools need to be closed because conditions are “unsafe” amid the coronavirus.

The United Federation of Teachers added that it would sue if any school where someone tests positive for the virus isn’t immediately shut down for at least 24 hours while the case is investigated, as per a recent state mandate.

“Enough is enough — stop the insanity,” UFT President Michael Mulgrew said.

A science teacher at one of the city’s most elite high schools, Stuyvesant, said at the press conference at UFT headquarters in Manhattan, “We understand [a shut-down] may have economic impact.

“We have faced 9/11, Hurricane Sandy … The response to those crises is that people came together. Coming together in this case is not an option.”

Mayor Bill de Blasio has said he is reluctant to close down city schools in part because of how it might affect crucial health-care and emergency workers who have school-age children.

He acknowledged Sunday that the city has no solid contingency plan should schools have to close.

Gov. Cuomo said separately Sunday that while closing down schools “sounds simple, it’s not simple.”

Repeating his own reluctance for New York City to shut its schools, the governor said, “If you close the schools and the children are home, a large percentage of the workforce may say, ‘I have to stay home to take care of my children.’

“Yeah, but we have essential workers who need to go to work: police people, firefighters. We can’t have … healthcare workers not come to work because they have to stay home.”

Additional reporting by Bernadette Hogan