CONCORD, N.H. — The lawyer for the graduate of an elite New Hampshire prep school who was convicted of sexually assaulting a younger student as part of a sordid campus practice of sexual conquest is using letters from his parents and classmates in a plea for probation instead of prison.

Twenty-year-old Owen Labrie of Tunbridge, Vermont, faces up to 11 years in prison when he is sentenced Thursday afternoon. Because he was convicted of using a computer to lure the 15-year-old girl to a sexual encounter at St. Paul’s School, he also will be required to register as a sex offender for life. Labrie was 18 at the time.

He will be given the opportunity to address the court before he is sentenced.

In documents filed Wednesday, defense attorney J.W. Carney Jr., said Labrie already has been punished — shunned by his alma mater and losing a full scholarship to Harvard, dashing his dream to attend the college’s divinity school.

His mother, Denise Holland, wrote in a letter to Merrimack County Superior Court Judge Larry Smukler that her son “has been punished beyond a degree that anyone else could possibly understand, but I see it in the fear and sadness in once-bright and joyful eyes.”

Dr. Edmund Piper, a clinical psychologist who has been treating Labrie for 13 months, called him “remarkable” and “mature beyond his years intellectually and responsibility-wise.”

A former female classmate called him “the kindest, most brilliant and most authentic friend I have,” adding that his conviction has not changed her opinion.

Besides the felony, Labrie also was convicted in August of three counts of misdemeanor sexual assault and one count of child endangerment.