Well, you two seem to be taking different definitions of "consent". It's true in America that people who are underage don't have a right to give their consent to much of anything. But a 14-year old is better informed than a six-year old. The 14-year old boy knew what he was doing, and he and the teacher both knew it was illegal. What I believe nik0tine is saying (correct me if I'm wrong) is that he wanted to have sex with his teacher. She didn't force him into it. And, the article wasn't exactly in-depth. We don't know who started the relationship, if it even happened.
