A 17-year-old student at Mount Lebanon High School has been charged in juvenile court with raping a girl in his car, sexually assaulting another at his home and sending threatening text messages to a third.

School officials said they're cooperating with the investigation even though none of the alleged incidents took place on school property.

Police said they began investigating a report that the boy raped a girl in September and later learned that he assaulted the second girl in August 2010 and sent the threatening texts a month later.

The boy is not being identified because he's held in a juvenile detention center, and police are not saying if the alleged victims also attended the high school or knew the boy in some other way.