ALLENTOWN, Pa. (AP) – A Pennsylvania high school teacher has been charged with having sex with a minor female student he began tutoring earlier this year.

The Lehigh County district attorney says the investigation began when the girl’s parents found inappropriate cellphone messages from 34-year-old Christopher Johnson on April 2.

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He was suspended three days later from his job as an English teacher at Parkland High School in Allentown and on Thursday surrendered on charges of institutional sexual assault, corruption of minors and unlawful contact with minors.

Institutional sexual assault makes it illegal for teachers to have sex with students because of the authority teachers have, whether or not the relationship was consensual.

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Johnson’s attorney didn’t immediately return a call for comment Friday.

Johnson faces a preliminary hearing April 20.

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