In my country it would be legal, as the legal age of consent is 16. It's very weird that a woman that age wants a boy aged 16, but I don't think it's necessarily worse that he has sex with an older woman as opposed to a girl his age. I was attracted to women who were at least 30 in that age, those I told rejected me because I was too young(and possibly several other reasons..) I never thought they saved me from sexual traumas. Did they?
I'm not sure what the attraction to students is... perhaps the fact that it's illegal, maybe that's what turns people on. But man that's a high price to pay - lose your job, your right to practice teaching and your reputation.