William Burke, a school administrator at John Bartram High School, was hospitalized at University of Pennsylvania Medical Center after being shot in the thigh. His injuries are not believed to be life threatening. Burke is 61 years old, police say.
Police spokeswoman Carmen Torres says Burke was shot just after 10 am ET.
The same bullet that hit Burke also went through the sole of a teacher's shoe. That teacher, who was not immediately identified, was not injured.
After the shooting, witnesses said the suspect tried running into other classrooms but students held the doors shut. The suspect was later apprehended about a block away from the school. Police also recovered a gun believed used in the shooting.
No charges had been filed as of late this morning. Torres would not identify the suspect.
An earlier, unconfirmed report said a second suspect was held by police.
The fight apparently broke out in a classroom, where the teacher called for aid from the principal's office.
Sophomore Richard Dorsett, 17, said he was in a classroom when he heard one shot followed by screaming in the hallway. Dozens of students left the school building, though officials said they were not closing school until 1 p.m.
"I got to get out of here. That's what I was thinking," Dorsett said. "I saw one of my closest friends come in crying."
Dorsett's mother, Cynthia Dorsett, 35, rushed to the school after she heard about the shooting.
"I feel sorry for the victim but I also feel sorry for the students. If they used the metal detectors the way they are supposed to be used, this wouldn't have happened," Dorsett said.