After tossing back beers, shots and club soda with at least one other teacher and an assistant principal, the tipsy staffers headed about a half-mile back to school to watch SING!, a musical competition that has been a school tradition for decades.

The duo sat through part of the show, and then disappeared, sneaking up to room 337 where Mauro usually taught French, according to the documents obtained by The News under the Freedom of Information Law.

Their apparent tryst in the darkened room was abruptly interrupted about 8:50 p.m. by two handymen who opened the door and made a startling discovery – “a woman lying on the floor naked from the waist up.”

“Oh, s—!” one of the teachers yelled out.

A school safety agent was summoned and arrived in time to catch the pair “naked” – one “on her knees” and one “lying on the floor,” the documents show.

“One female had on pants with no shirt; she was putting on a white bra with one breast still hanging out,” Waite reports.

An assistant principal was called in to identify the pair, arriving in time to catch Brito still “buttoning her shirt” and “putting on her shoe.”

Mauro and Brito were cited for “inappropriate sexual behavior in Room 337″ and drinking an “undetermined amount,” and they were charged with misconduct.

“As a teacher, you are expected to be an exemplary role model for other staff members and for students,” wrote Waite in her letter. “Your lack of judgment constitutes conduct unbecoming of an educator and warrants termination.”

Their attorney, Mark Nussbaum, pointed out yesterday that the documents contain allegations that the teachers haven’t had the opportunity to contest yet. They have filed requests for formal hearings, he said.