The case hinged on what was known as a tradition known as the "senior salute" among older pupils, in which they competed to spend time with younger students, often for sexual purposes.
Senior students vied to "slay" as many girls as they could - a term which meant anything from kissing to sex.
Labrie, the court was told, was a member of a small Facebook group, called "Slaymakers Anonymous" whose members would allegedly map out their conquests in a diagram on a school wall before it was painted over.
In this case Labrie was accused of forcing himself on the girl in a noisy mechanical room two days before he graduated in 2014.
His accuser admitted she had accepted Labrie's invitation to meet. She had expected their contact to be limited to kissing.
But J.W. Carney, Labrie's lawyer said the encounter stopped short of intercourse, having decided "it would not be a good choice for me".
Labrie admitted in evidence to boasting to other students that he had sex with the girl, but insisted that this was merely an empty act of bravado.
After the verdict was announced, the girl's family said in a statement: "Today, a measure of justice has been served for victims of sexual violence.
"Owen Labrie was held accountable in some way by a jury of his peers for the crimes he committed against our daughter."
The school insisted that it only became aware of the "Senior Salute" in 2013 and that it did not reflect its culture.
In an open letter to students, parents and alumni, Michael Hirschfeld, the school's rector and James Waterbury, the president of the board of trustees said: "The behaviour was never condoned by the school and we took action when it surfaced."
