38-year-old Charles Coursey of Milton, Del. is a teacher at Sussex Technical High School in Georgetown, Del.
Delaware State Police say school administrators contacted them Wednesday alerting them to the alleged relationship.
Police determined that the relationship had been going on since the beginning of the month. It involved alleged meetings between Coursey and the victim at various locations in Sussex County.
Coursey was arrested and charged with 3 counts of sexual abuse of a child and 4 counts of unlawful sexual contact.
He is being held at the Sussex Correction Center on $17,000 secured bail.