RUTHERFORD — A 14-year-old student repeatedly stabbed a middle school principal during graduation practice on Friday, police said.

Police arrested the teen at Washington School after getting a call about the attack at 9:30 a.m.

Police said Union School Principal Kurt Schweitzer was with his school's eighth graders rehearsing at Washington School when the teenager rushed across the gym and struck a folding knife several times into Schweitzer's chest. Schweitzer suffered non-life-threatening injuries, police said.

Police said the student then turned around, dropped the knife and placed his hands in the air.

A teacher escorted the student outside until police arrived.

Police did not say Friday afternoon whether they knew what motivated the attack.

The teen was charged as a juvenile with second-degree and third-degree aggravated assault and third-degree and fourth-degree weapons offenses. He remained in custody late Friday afternoon.

Because he is underage, police did not publicly identify the student.

Police said they will have "have a presence" at the graduation on Wednesday evening even though the department "is confident there are no remaining threats to any students or faculty."