@user171 Losing job is one thing. He'd probably be unable to find any teacher job in the future, his public image would be destroyed, he'd have to move out - probably somewhere far away, his family and friends would be affected and there's probability of criminal record. Sure, power of boners is stronk, but when your entire life is at stake it's probably hard (hah!) to get an erection...
@thaeril There's also the bit that we're looking at stylized characters, teenagers look incredibly young as you get older and it's easy to have that wall up in reality when most of em look like kids lol.
@Kalocin Yeah, I didn't even mention moral consequences... It depends on a person, some people would probably be fine with it but as a teacher, you'd probably feel like a human failure (if you are a decent human being to begin with) after banging a teenager and your student.