Three teens have been charged with second-degree assault following a fight at Lansdowne High last week.
Police said the teens came into a classroom and attacked an 18 year old girl. The suspects were all cousins, a 13-year-old boy and two 17-year-old girls.
The fight was broken up by a school resource officer.
But police don't think all of them were Landsdowne students, but were let into the school by a student.
The school system says all exterior doors should be locked and visitors are expected to check in at the main office.