Michigan law appears to make it a crime for a teacher to have ANY sexual relations with someone who is a student (even homeschooled) under the age of 18. So, if he wants to risk jail and the loss of his career, he can be a complete moron and maintain this perverse relationship. Your "friend" is p[laying with a man's future and may be getting some sort of twisted sense of adventure out of the forbidden nature of their illicit affair.