The star football coach preys on young high school girls. Many people, both students and faculty members, know it. No one does anything about it, though. Finally, he chooses a student whose parents plan on stopping him once and for all, and who intend to make the negligent school pay, too. That's more towards the end of the movie, though. Most of the movie shows how the coach grooms the girl, then hangs out and provides alcohol to her and her friends, and then starts kissing and having sex with her; even in school and in his own home when his wife and children are sleeping. He obviously wants to believe he's still a teenager. One of the saddest parts of the film is watching how the girl is treated by students once the coach has to pay the piper. A sad but true story.
P.S. 8/24: To learn more about the real case this movie was based on, look for the TexasMonthly article entitled "The Seduction of Jane Doe", dated November 1994.