CONCORD, N.H. -- A graduate of an exclusive New England prep school was cleared of felony rape but convicted of misdemeanour sex offences Friday against a 15-year-old girl in a case that exposed a campus tradition in which the oldest students competed to see how many younger students they could have sex with.

Nineteen-year-old Owen Labrie was accused of forcing himself on the girl in a dark and noisy mechanical room at St. Paul's School two days before he graduated in 2014.

He wept upon hearing the verdict.

Labrie, who was bound for Harvard, was acquitted of the most serious charges against him -- three counts of felony rape, each punishable by 10 to 20 years in prison -- but was found guilty of three counts of misdemeanour sexual assault and other offences.

Each count carries up to a year behind bars. Labrie could get as much as 11 years in prison at sentencing Oct. 29. He will also have to register as a sex offender for the rest of his life.

The 159-year-old boarding school has long been a training ground for politicians, Nobel laureates, corporate executives and other members of the country's elite. Alumni include Secretary of State John Kerry. Students pay $53,810 a year in tuition, room and board.

Labrie, an aspiring minister, testified that he stopped short of intercourse because he suddenly decided "it wouldn't have been a good choice for me."

In his testimony, Labrie acknowledged bragging to friends that he had intercourse with the girl, but he said that was a lie told to impress them. He also admitted deleting 119 Facebook messages, including one in which he boasted that he "pulled every trick in the book" to have sex with her.

The girl, now 16, said she willingly went with Labrie after he invited her to take part in Senior Salute, a tradition she said she knew about. But she said she was prepared for kissing at most.