The fire was reported shortly after noon in the 6100 block of Stenton Ave.
The fire was reported to be in room 300 of the building. Officials say books were set on fire inside an unused classroom. The fire marshal is trying to determine if it was set intentionally.
The building was evacuated and most students were dismissed shortly thereafter. Special education students were relocated to another facility.
One pregnant person was taken to the hospital to be check, but there were no other injuries reported.
A spokeswoman for the Philadelphia School District calls the fire "serious."
Parents can call 215-400-INFO for more information.