Atlanta police are investigating an allegation that a 17-year-old boy sexually assaulted a 15-year-old girl Tuesday at Crim High School.

The girl told police she and the boy were on the auditorium stage doing homework shortly after 3 p.m. He was supposed to be helping her, but began trying to kiss her, police said.

The girl immediately said no and pushed him away, police spokeswoman Officer Kim Jones said.

The girl told police the boy touched her on her buttocks and pulled her toward him. The girl said she repeatedly told him to stop and tried to pull away. The boy’s grip tightened, and he forced her to the floor and sexually assaulted her, Jones said.

After the alleged assault, the boy got up and ran out the school. The girl went and told a friend, who found a teacher and disclosed what happened, police said.

When the girl’s mother got to the school, she was advised to take her daughter to Children’s Healthcare of Atlanta at Hughes Spalding for a sexual assault examination, police said.

“This is a police matter being investigated by the Atlanta Police Department,” said Kimberly Willis Green, spokeswoman for Atlanta Public Schools.

Atlanta police originally said the incident occurred at Carver High.

This is second time since March that police have investigated an alleged sexual assault at an Atlanta high school. A student was accused of sexually assaulting another student at BEST Academy, an all-boys school.