Authorities say a 13-year-old student brought a loaded gun to Ambridge Area Middle School Wednesday and threatened a classmate.
The Beaver County District Attorney said the teen had his parents' gun, which was supposed to be locked up at their home.
The threat was reported to the principal by another student, who called police.
Ambridge officers found the gun and cleared the school.
The student was arrested and is not being charged as an adult.
Ambridge Area students are in flexible instruction Thursday. The district plans to reopen school on Friday.