Three years after the alleged incident occurred, a Montgomery County schoolteacher was charged this morning with failing to report that a former student had informed him she had been raped.

Frank R. Mercon, 40, a health teacher at Upper Perkiomen High School, was arraigned before a Red Hill district magistrate and released on $10,000 bail.

The alleged incident occurred three years ago, but was brought to the attention of Berks County officials only recently by an unidentified person, said county District Attorney Risa Vetri Ferman.

In 2010, the former student informed Mercon that the year before she was the victim of a "date rape" by an adult male at the Penn State Berks County campus, according to the affidavit of probable cause. At the time of the alleged rape, she was 15.

During the investigation, it was learned that the alleged victim had informed Mercon of the incident in a written note because "she didn't want to say it out loud," the affidavit said.

Mercon told her it was too late to report the incident to police, and in the presence of the victim and a friend burned the note in a science lab, the affidavit said.

County District Attorney Risa Ferman said Mercon had a legal obligation to report the rape allegation.

"The most basic purpose of child abuse reporting requirements is the protection of children," she said. "Under the law, teachers have special legal obligations to report suspected abuse. The charges filed today reflect a serious failure to protect a teenage girl by a person she trusted."

The school's principal said that last year he had informed teachers of such responsibilities.

Mercon was arraigned before District Judge Catherine M. Hummel-Fried and charged with failure to report suspected child abuse.

Mercon's attorney, Marc Neff, of Philadelphia, said, "It is an unusual case."

"We're going through the documents and investigating," he said. "We will do our due diligence and try to sort this out."

The school district said that it "does not comment on matters involving specific employees or students at the allegation stage," but would do "everything in its power to cooperate with this investigation."

The preliminary hearing is set for Oct. 19.