PITTSBURGH — A school board member has resigned over what he calls a “major difference of opinions” between himself and the school district over the handling of sex allegations against two teachers.

Joseph Tommarello submitted his letter of resignation following Plum High School’s graduation ceremony Friday, citing the charges against 40-year-old Joseph Ruggieri of New Kensington and 38-year-old Jason Cooper of Verona.

Each is accused of having had an improper sexual relationship with a female student. Another teacher, 40-year-old Drew Zoldak, is accused of having intimidated one of the victims.

Tommarello said he warned administrators nearly three years ago about a possible inappropriate relationship between Ruggieri and a student. He said he therefore lacks the “full confidence” in the district’s leadership that has been expressed by the school board president.

“I no longer feel comfortable being in a situation where my morals and values are being compromised by being told to remain silent and to show full confidence in our leaders,” Tommarello wrote.

School board president Sal Colella said in a statement he was disappointed both by Tommarello’s decision and by the contents of his letter.

He said the district began an investigation immediately being informed by Tomarello three years ago about the possible inappropriate relationship, but “the student and family dismissed the allegations as false.”

Colella said Tommarello never expressed any of his frustrations to the board — and he also said Tommarello had attended just four of the last 22 school board meetings.