One student was injured and nine were arrested in a large brawl in a second-floor hallway at Frankford High School on Wednesday morning.
The student suffered a cut above her left eye and was treated at the school by paramedics, police said. There were no injuries to staff.
The fight broke out among a large group of female students, city police said. Police were not sure how many students were involved.
A teacher said about 50 students appeared to have congregated in the area of the fight. All security officers were called to the floor over the loudspeaker, said the teacher, who asked not to be identified for fear of reprisal. Students were rampaging in the halls and hitting security officers, the teacher said.
"It was just an out-of-control crowd," the teacher said.
District spokesman Fernando Gallard said the fight broke out between two groups of girls at the change of classes. He said the district was investigating and the outcome would determine whether the nine face disciplinary action.