PLUM (KDKA/AP) — Charges that a western Pennsylvania high school teacher had sex with an 18-year-old student have led to an investigation that another teacher had sex with yet another student.

Jason Cooper, 38, was arrested Wednesday on charges that he had an inappropriate sexual relationship with an 18-year-old female student.

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Sex between a teacher and an adult student is illegal in Pennsylvania, because the student isn’t considered legally able to consent given the student-teacher relationship.

Cooper was charged with institutional sexual assault, corruption of minors and furnishing alcohol to a minor.

The encounters allegedly took place at both the high school and at Cooper’s home.

The Plum High School principal was tipped off about the relationship by a school source, and an internal investigation led to Plum Police being called in.

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Cooper’s attorney, Michael DeRiso, said in a statement: “I’ll fight to get the charges against Cooper dismissed. The alleged victim was 18-years-old, and by law, not considered a minor.”

Meanwhile, the school and police are investigating a second possible inappropriate student-teacher relationship at the high school.

Sources say the second investigation involves a teacher and a 15-year-old girl. Charges could be filed in the second case as early as Thursday.

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