A teacher at a charter school in Chester County has been charged with institutional sexual assault after police say she had sex with one of her students.

Katie L. Cross, 31, of the 1200 block of Monroe Avenue in Phoenixville, turned herself in to West Chester police Thursday.

She also faces charges of corruption of minors, endangering the welfare of children and related charges.

Cross was the 17-year-old student's Language Arts teacher at Collegium Charter School in Exton. The student told police he had been in a physical relationship with Cross since February.

The school has suspended Cross until further notice.

On July 1, an East Bradford resident called West Chester police to report a suspicious vehicle in which an intimate encounter was taking place, according to a criminal complaint.

Police arrived to find Cross and the student shortly after 8 p.m. in the 1400 block of Scenic Drive.

The student said that Cross picked him up and drove them to secluded areas on two occasions, according to a criminal complaint. The student also said he and Cross had kissed in her classroom several times.

Cross was released on $150,000 unsecured bail Thursday. A preliminary hearing is scheduled for Tuesday.

- Michaelle Bond