Andrew Chrzanowski, 29, of the 300 block of Tollhouse Place, was arrested on Thursday afternoon.
He has been charged with Sexual Abuse of a Child by a Person in Authority and Continuous Sexual Abuse of a Child.
Chrzanowski is a teacher at Caesar Rodney High School. Police said he had an ongoing sexual relationship with a 17-year-old female student.
Bond information for Chrzanowski is still pending.