The 19-year-old is convicted of aiming an air pistol in through a window of a classroom.
The plot frightened the teacher and the students who evacuated the classroom.
The man denies the crime and says that he did not deliberately aim the weapon at anyone, but that a friend had his air pistol with him to school and that he tried to hold it for a while.
The 19-year-old has now been sentenced to a suspended sentence and a 130-day fine.
He must also pay damages to three students to whom the weapon was aimed.
They get 10,000 kroner each.