The rape happened in a bathroom at the Vare Recreation Center on Morris Street Wednesday afternoon, investigators said.
A 14-year-old girl, at student at Audenreid High School, says she was attacked by a 14-year-old boy from the same school.
The victim is new to the school, police said, which just started back on Monday.
Action News was there as police arrived at the school to pull attendance records. They are also expected to pull surveillance video from the rec center.
According to police, the victim told investigators that the suspect had been "hitting on her" and saying "crude things."
Then, the girl told police, the boy demanded she go to the rec center on Wednesday or he would kill her.
The two walked several blocks to the center, the girl allegedly told police. Once there, she said, he pulled her into a bathroom and raped her.
Investigators went on to say that some adults in the rec center heard screaming coming from the bathroom. They forced their way in, catching the suspect in the act.
The suspect then ran off.
The girl was treated at Saint Christopher's Hospital.
In a statement, management at Universal Companies, which runs the school, said:
"We were shocked and saddened to learn that one of our freshman scholars was allegedly assaulted at one of the area recreation centers by a fellow classmate after school yesterday.
Our hearts go out to the victim and her family and we will not tolerate nor accept this type of behavior in our community.
We are taking the necessary steps to ensure the safety in school and out of school for all our scholars which includes encouraging that our scholars not travel alone (use the buddy system) and to alert staff of any/all potential threats".
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.