A graduate of an elite New Hampshire prep school faces lifetime registration as a sex offender after a judge on Tuesday upheld his conviction for using a computer to lure an underage girl to a sexual encounter as part of a sordid game of conquest.

Owen Labrie, of Tunbridge, Vermont, was convicted in August after a trial that exposed a practice among students at St. Paul's School known as Senior Salute, in which graduating students try to have sex with younger classmates.

Merrimack County Superior Court Judge Larry Smukler upheld the felony conviction of using a computer to lure the girl to the encounter.

Last month, Labrie's lawyers asked the trial judge to throw out the conviction or not require him to register as a sex offender for life.

"If he had merely called the 15-year-old on the telephone or spoken to her in person, there would be no additional crime," his lawyers wrote. "Yet because he prearranged the encounter through email and Facebook, he will be subjected to the scrutiny and humiliation of sex offender registration for the rest of his life."

Prosecutors countered that when the crime occurred, Labrie was an adult in the eyes of the law.

"He used the Internet to exploit (the girl's) youth and innocence in an attempt to lure her into sexual activities," prosecutor Catherine Ruffle said.

Smukler rejected arguments made by Labrie's lawyers that the computer charge shouldn't have been applied to him because it was intended to protect children from older sexual predators and strangers who used computers to lure them to sexual encounters -- not from high school classmates.

Ruffle said Tuesday she was pleased with the judge's ruling.

Labrie's lawyer, J.W. Carney Jr., said he was disappointed by Smukler's ruling and would appeal to the New Hampshire Supreme Court. He also said he would seek clarification of the computer statute from the legislature or clemency from Gov. Maggie Hassan.

The sexual contact occurred just before graduation in 2014, when Labrie was 18 and the girl 15. Labrie had been bound for Harvard University and planned to take divinity classes before his arrest put everything on hold.

Labrie took the girl first to the rooftop of a nearly deserted academic building then led her to a dark mechanical room where they consensually kissed and touched each other. The girl testified that he then raped her. Labrie insisted there was no intercourse but acknowledged he had boasted to the contrary to friends in sexually charged emails and social media posts that were shared with the jury.

He was acquitted of the most serious charges against him, three counts of felony rape, but convicted of misdemeanor sexual assault and child endangerment charges.

Labrie, now 19, faces a sentence that could range from probation to up to 11 years in prison. Labrie, who had no criminal record, will be able to petition the court to be removed from the sex offender list 15 years after the end of his sentence on the felony charge. The misdemeanor convictions require him to register for at least 10 years.