An elite New England prep school was sued on Wednesday by the family of an underage female student who was lured into a sexual encounter with a graduating upperclassman.

The federal lawsuit alleges that administrators at St. Paul’s School in Concord, New Hampshire, knowingly tolerated a tradition known as the “senior salute,” in which senior students sought to have sexual encounters with as many freshmen as possible.

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Former St. Paul's student Owen Labrie was found guilty in 2015 of having sex with the girl in an encounter days before his 2014 graduation. She was 15 at the time and below the legal age of consent.

He was also found guilty of a felony charge of using a computer to lure the teen. The high-profile trial shone a harsh light on the culture of the elite 160-year-old school, whose alumni include U.S. Secretary of State John Kerry.

The jury acquitted Labrie of felony rape charges. Labrie, now 20 and free on bail, is seeking a new trial.

The lawsuit alleges that the girl was sexually assaulted "as a direct result of SPS' fostering, permitting and condoning a tradition of ritualized statutory rape (referred to as the 'Senior Salute') among its students and SPS' utter failure to meet its most basic obligations to protect the children entrusted to its care."

A St. Paul's School representative said in a statement the school would vigorously defend itself.

"We categorically reject any allegations that St. Paul’s School has an unhealthy culture. The safety of our students has been and will continue to be the highest priority for our school,” the statement said.

The law firm representing the girl’s family, Silverman, Thompson, Slutkin and White, alleged that Labrie was part of clique of student leaders and athletes who called themselves the “Slaymakers.”

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The group operated largely in the open, the suit charged, with a set of keys exchanged among them for places on campus where trysts took place.

The suit filed in U.S. District Court in New Hampshire seeks unspecified damages on several legal grounds, including negligence and breach of fiduciary duty.