PHILADELPHIA -- An outraged mother says that her 12-year-old son was raped by an 11-year-old classmate at John B. Stetson Middle School in Philadelphia.

The 11-year-old has been charged with involuntary deviate sexual behavior.

The 12-year-old said it all started with a fight over a ball on Tuesday. Minutes later, the boy claimed, he was being sexually attacked.

The alleged victim's father said that he is sick to his stomach over the attack.

"It hurts me. He raped my son, he raped me, too," the boy's mother said.

The parents of the alleged victim said the two boys got into a dispute over a ball in the fourth-floor bathroom of the school. The 11-year-old male student then allegedly chased the 12-year-old inside the third-floor fire escape and sexually assaulted him.

"The boy was choking him, threatening him, and then made him get down on the ground and pulled down his pants -- over a handball," said the alleged victim's mother.

"I'm upset with the school. They couldn't see two children fighting and somehow they get into the fire escape. How did that happen? How do you go in there without nobody noticing? No alarm systems, no cameras," the boy's mother said.

WCAU-TV talked to the alleged victim and asked him what he thinks should happen to his accused attacker.

"Go to jail for the rest of his life," the boy said.

Late Wednesday afternoon, Edison Schools spokesman Richard Barth said there are no cameras where the alleged rape occurred.

"We are -- Edison Schools and the school district of Philadelphia, which are partners working at Stetson Middle School -- are conducting an internal investigation," Barth said.

The CEO of the Philadelphia school district, Paul Vallas, questioned how such a crime could happen.

"My reaction is one of outrage. If anyone has failed to follow procedures, they will be fired. It is a simple as that," Vallas said.

"I'm thinking they're safer in school and home than in their streets. And they're not, they're not safe," the alleged victim's mother said.

The alleged victim has been allowed to transfer to another school. The boy accused of the attack has been expelled. Crisis counseling has been offered to both families.