In 2004 An unsigned letter tipped off school officials who contacted police, but at that time they didn't have any supporting evidence. That was the end of the case until earlier this month when a student confided in the principal.
Here's a description from the Minnesota Coalition Against Sexual Assault that likely applies in this situation:
Many people dismiss this type of coercion as either harmless or annoying but never criminal . However, manipulation and abuse of power definitely harm those who are misused -- be they male or female.
Sexual Coercion: Compelling someone to submit to an unwanted sexual act by intimidating, threatening, misusing authority, manipulating, tricking, or bribing with actions and words. When a person is coerced, she or he has not given consent.