It happened during the first day of summer school on Tuesday.
Police are using two videos that circulated on social media as part of their investigation.
Two teen girls were assaulted during the incident.
"Two of the females had some head and neck injuries from being assaulted by at least three other girls in this incident," said Philadelphia Police Deputy Commissioner Frank Vanore.
Mecca Robinson is a guardian of a child that goes to the school. She also runs a nonprofit aimed at helping homeless youth. She has rallied the heads of fellow organizations that also work with Philadelphia teens.
"We met with the principal today. I asked her, 'What do you need from the community?'" said Robinson.
Ernie Bristow is one of several youth leaders who answered Mecca's call for help. They met outside the school Thursday morning.
"They asked for support, now we came out. We're building to continue (support) because it's not a one-day event," said Bristow.
In the meantime, the investigation is ongoing. Police believe this began with a verbal altercation that became physical and spilled into the hallway.
"We're doing interviews, looking at video on social media to see who else we could identify and talk to," said Vanore.
The School District released this statement on the incident:
"Since we are not the originators of the video, we cannot verify its authenticity.
The School District of Philadelphia is aware of an altercation that occurred at Benjamin Franklin High School. The District is committed to providing safe and welcoming schools and summer programming. Incidents that potentially compromise the safety of students and staff are taken very seriously. The District's Office of School Safety is conducting a thorough investigation, while Philadelphia Police investigate. Appropriate disciplinary action will be taken in accordance with applicable District policies."
Philadelphia police has a detective assigned to the school district.
The two victims were sent to the hospital and have since been treated and released.