I think that any case of teacher-student relationships should be investigated, because I have heard/read numerous accounts of the preppy, spoiled little b*tches falsely reporting sexual abuse by teachers because said teachers gave the girls bad grades. Then an innocent teacher's life and career may get ruined (as well as many other possible job endeavors because being labeled a sex offender screws you over in so many occupations).
I just think it sucks as well when kids will put the moves on a teacher and then the teacher gets blamed, even if they don't respond to the student's advances. But teachers who do try to or succeed in getting involved romantically with students should definitely be punished - they aren't in an educational setting to hunt for booty.
I hate to admit to this, but I might have pursued my high school sociology teacher after graduation if he wasn't married. He was a really cool guy and very smart and funny (and very handsome)...then he spawned. Barf - big turn-off to me. Wifey can have him