A 22-year-old Mystic man pleaded guilty this morning in New London Superior Court to stabbing a teen-age boy last year at Northeast Academy in a dispute over a girl.

Joseph LaMarche will be sentenced Sept. 27 to up to three years in prison for first-degree assault.

According to prosecutor Theresa Anne Ferryman, LaMarche and the 14-year-old victim agreed to meet on Oslo Street to talk about a problem with a girl. LaMarche, saying he knew he would probably regret it, told the boy he had stolen his girlfriend then stabbed him in the chest with a knife.

The victim recovered and is expected to attend the sentencing, where defense attorney Margaret Steele will have the opportunity to argue for a shorter prison term. Judge Patrick J. Clifford told LaMarche that the maximum sentence he would impose is eight years in prison, suspended after three years served, followed by three years probation.

Neither LaMarche nor the victim were enrolled at Northeast Academy, a public elementary school in Groton.