A teacher at Brooklyn Tech High School — one of the largest in the nation — has self-reported a positive coronavirus test, The Post has learned.

Principal David Newman sent an email to parents late Thursday to alert them of the development.

“I am writing to inform you that a member of our school community has self-reported that they tested positive for COVID-19,” the administrator wrote. “A disinfection of the school building has been completed in accordance with New York State Department of Health guidelines. As a reminder, the DOE routinely conducts deep cleanings in your school.”

The announcement sparked widespread unease in the Brooklyn Tech community given the building’s immense enrollment of nearly 6,000 kids.

“There is massive concern right now,” a parent told The Post Friday.

“The fear is that the school is so big that there is the potential for a lot of infections,” another parent said. “People are worried.”

But another parent said that it was only a matter of time before there was a coronavirus case in the building and that he was taking it in stride.

“We are just following all the precautions right now and doing what we can,” he said. “I’m surprised that it took this long.”

Like all other Department of Education schools, Brooklyn Tech has ended in-person instruction and will launch a remote learning plan Monday.

“Nothing matters more than the health and safety of our staff and students, and we are committed to keeping our school community fully informed,” Newman told parents.

Along with Stuyvesant and Bronx Science, Brooklyn Tech is considered one of the city’s most competitive high schools.