A Bronx teacher who's been educating teens about HIV and AIDS prevention for decades says he has no choice but to retire.

It's one of the last times Tom Porton will walk through these doors.

The English teacher of 47 years who started a teen peer education program about HIV prevention is retiring.

"It's not something I started out this term wanting to do," Porton said. "I expected to hit at least 50 years."

But Porton says he feels he has no choice.

It all started on World AIDS Day in December, when as NY1 first reported, Porton's principal told him to stop handing out this HIV prevention flyer.

Porton has handed out the flyer for 25 years and says the message is especially important in the Bronx where many teens do not practice safe sex and the rate of HIV and AIDS infection is high.

But the new principal at the Monroe Academy for Visual Arts, one of several schools in the building, told Porton that it was inappropriate.

At the time, former students contacted by NY1 praised Porton.

"He saved my life and I owe everything to him and he has saved hundreds if not thousands of teenagers," said one student.

In a statement given to NY1 then, the principal said he'd discuss the matter with Porton, but never did.

"That was the beginning of a whole bunch of hostility that I've experienced from this new administration which was one of the reasons I considered retiring," Porton said.

Porton says he was given extra classes to teach, and stripped of a class that involved students in activities in the community.

He complained to the Education Department but got no reply.

"Obviously everything is acceptable in their eyes and a veteran teacher can be treated this way," he said

So Porton decided to retire, to the dismay of students and staff, who showed him support on Facebook.

"From what I hear, it's hurting a lot of other people," he added.

Porton says he will continue his HIV work — for example, hosting an annual HIV/AIDS conference in May.

But his last day at Monroe is February 1.

In a statement provided to NY1, a DOE spokesperson said, "Teaching students about healthy relationships and HIV/AIDS prevention strategies is a critical goal for the DOE, and we thank Mr. Porton for his years of tireless dedication.”  The agency added that given a wide array of options for students at the school to learn about safe sex practices, the principal felt that the most appropriate place for sexual education was with a licensed health professionals with training in the area."