It happened around 11:15 a.m. at the University City High School on the 3600 block of Filbert Street.
School officials say that's when a group of about 10 students began fighting in a second floor hallway.
A 17-year-old junior was taken to Children's Hospital with a possible concussion due to injuries to the head.
There is no word yet on if anyone will be charged in this fight.
School police are investigating.
