Really? Suicide?
Kids can be fragile. Some 15-year-old boys are emotionally ready to have athletic, emotionless sex with their teachers (or at least, keep their emotions under control). Others are not.
Maybe he was fine for having sex, but getting cut off drove him to depression and suicide. I'm not saying it's a logical choice, but kids don't always have a logical perspective and time seems a lot longer when you're young.
He thought that he was the only one. When the news story broke, he fell into a deep depression (acording to the court transcripts) and killed himself. This teacher apparently tempted all of her male charges. Reports indicated that she arranged the classrom seating assignments so that all males were in the front rows. Also, she wore short skirts and would sit on the edge of her desk so as to display either provocative knickers or the lack thereof. As the trial proceeded, one of the lads disclosed that he and the teacher had sex in the classroom's supply closet. Taxpayer dollars at work.