Key, who is a language teacher at Haverford High School, had a sexual relationship with one of his male students, according to court documents.
Authorities say it all began when the boy, who was 16 at the time, enrolled in Key's after school program called the "Chinese Club."
Court documents stated that the two developed a relationship in October 2008 and they met at Key's home.
Last month, the boy came with his parents to the Haverford Township Police Department and told authorities about the relationship, police said.
According to court documents, Key told police during a recent interview that he should not have been involved with the student.
“I know that I should not have been involved with (the student), but the attention he gave to me made me to overlook the inappropriateness – naively. I understand that I am to have no longer any contact with (the student) which I will 100 percent abide by as I am deeply sorry for all the trouble I have caused. Our sexual contact was only twice," court documents show Key told police.
When we went to Key's Wayne home, the man who answered said Key was not home and closed the door.
Key has been indefinitely suspended from Haverford High. Authorities confiscated computers from both the teacher and student, and both machines are now part of the investigation.
The suspect is expected in court Thursday morning. Calls to the school district were not returned.