WYNCOTE, Pa. (AP) — Four female high school students have been arrested after seven teachers and three safety officers were injured trying to break up fights at a Philadelphia-area school.

The teachers' union told The Philadelphia Inquirer (http://bit.ly/2qGqxVs ) that a long-term substitute at Cheltenham High School was the most seriously injured, suffering a concussion when she was hit in the head by a student's elbow.

A school district spokeswoman says there were two fights on Wednesday, one in the morning and one at the end of the school day, each involving two students. All four were arre...