An "innocent" conversation between two Germantown High freshmen turned into a nightmare for a girl Friday morning, when the boy she'd been talking with attacked and raped her in the school's basement, police said.

Special Victims Unit Capt. John Darby said the students were acquaintances who'd known each other for a few weeks before the alleged attack.

The two met about 7:45 a.m. Friday and had "innocent contact" in a stairwell, Darby said. After the boy went down the stairs into the basement, the girl followed him and he raped her, Darby said.

"Ultimately at some point during that first class, the victim basically broke down and disclosed [the attack] to a teacher," Darby said.

The teacher alerted authorities, and police launched an "aggressive investigation," he said. Friday night, investigators submitted a probable-cause affidavit to the District Attorney's Office for the arrest of the alleged perpetrator and were in contact with the boy's family.

Accompanied by family members, he surrendered to police in the Special Victims Unit, on Lehigh Avenue near Front Street, Tuesday morning and was taken into custody.

He faces five felony counts and four misdemeanor counts on charges including rape and aggravated indecent assault. Police found evidence at the scene, but Darby did not specify what that was, citing the ongoing investigation. "What we do have is compelling," he said.

Authorities have not identified the youth, but school district spokesman Fernando Gallard said both he and the alleged victim were freshmen at the school.

Gallard said that he's unsure if Germantown High's principal has any outreach planned for the student body in the wake of the alleged attack but that the school district is ensuring that the girl has appropriate services and support.

Cops periodically get reports of rapes in schools, Darby said, but they generally are not as severe as Friday's alleged incident. n

Contact Morgan Zalot at 215-854-5928 or zalotm@phillynews.com, or follow on Twitter @morganzalot.