Mark Krolikowski has shoulder-length brown hair. He likes to wear multiple earrings and French manicure his nails. Students call him Mr. K.

Krolikowski, 59, taught for 32 years at St. Francis Preparatory School, a 140-year-old Catholic institution in Queens, New York.

Until August. That's when the school laid him off.

He alleges that he was discriminated against because he is transgender and that the school's attitude toward him changed in the eight months after he came out.

He recently filed a lawsuit saying the school and its principal, Leonard Conway, broke the law with his termination and that as a result, Krolikowski has been financially and emotionally distressed.

"We believe that this case has significant ramifications for the LGBT community and is a wakeup call to employers in terms of employment practices," said Krolikowski's lawyer, Andrew Kimler.

Conway would not comment but referred questions to his lawyer, Philip C. Semprevivo Jr.

Semprevivo said he could not discuss details of the case since it was in litigation but said Krolikowski was terminated legally.

"We deny all the allegations," he said.

In the meantime, former students of St. Francis launched an online petition that describes Krolikowski as a beloved and well-respected teacher and urges the school to apologize.

Cristina Guarino, who started the petition on Change.org, said Krolikowski always had a "feminine edge," though it was nothing shocking. Some students speculated on his sexuality and wondered whether he was gay.

"I really never questioned his gender identity despite his somewhat feminized looks," she said. "It just didn't seem to matter, and it never affected his teaching style or his opinions. He never imposed anything on us."

She said Krolikowski's sex education class called Human Sexuality and Love was one of her favorites during her four years at St. Francis. Krolikowski's gender identity never was an issue in class, she said. He was the kind of teacher who told jokes and acted silly in class to make students feel more comfortable talking about sex.

"I still laugh to this day when I remember it. Mr. K was someone who brightened our lives," said Guarino, who spoke with Krolikowski by phone this week.

He'd called her to thank her for the show of support through the online petition. He said he just wanted to make things right for him.

His account of what happened is described in the lawsuit.

Krolikowski began teaching at St. Francis in 1980. Aside from his regular classes, he volunteered to lead students in many extracurricular activities that included music, performance of school liturgies and an international night and graduation ceremony.

He says the school never questioned his abilities, loyalty or dedication to the Catholic faith. But that changed, according to him, in October 2011, when he was summoned to the principal's office to meet with Conway and Assistant Principal Patrick McLaughlin.

Krolikowski says he was informed then that a parent of a freshman student had complained about the teacher's appearance.

He admits his appearance is considered unconventional. But he said he always wore a suit and tie, and his personal grooming conformed to school standards. Former St. Francis students who have signed the petition agreed with that description.