I don't think the problem is a question of unequal footing between teacher and student. For me the issue is that most girls are brought up to be wary of sex while boys are brought up to be more open and more aggressive about sex. This makes the situation completely different when it's a male student rather than a female one. While for a male teen, consensual sex with someone older might healthy, and even a major self confidence boost, for a female teen, it brings with it a much bigger and more dangerous load of emotional baggage. Of course, these issues will likely be exacerbated by the teacher's position but, again, those issues are a direct consequence of the child's mores.
I hope this doesn't make me sound like I support child molesting, or something.