CONCORD, N.H. — Appearing on a video screen, the victim of a sexual assault by an older student at one of the nation’s most exclusive boarding schools asked a judge here on Thursday to make sure her assailant was held accountable for a crime that, she said, had left her numb.

“What he did to me made me feel like I didn’t belong on this planet and that I would be better off dead,” the girl said.

She added: “Without just and right punishment, I really don’t know how I’ll put one foot in front of the other. I don’t want to feel imprisoned for the rest of my life. I want to be safe again. And I want justice.”

At the end of a nearly three-hour hearing, Judge Larry M. Smukler of Merrimack Superior Court turned to the convict, Owen Labrie, once a star student at St. Paul’s School just a few miles away. “You’re going to do a year in the House of Corrections and probation,” he told Mr. Labrie. “That’s the bottom line.”