Statutory rape is a crime either way, but society tends to view the statutory rape of a consenting male minor as less severe than the statutory rape of a consenting female minor.
I think part of it is that we're socialized to see males having sex as some sort of triumph, victory, or a rite of manhood, while we're also socialized to see the reverse as something much more significant, as there is very little change for males when they lose their virginity, unless they happen to catch an STD, as opposed to the potentially large changes when a female loses their virginity(hymen breaking, possibility of pregnancy).
And much as I know both are wrong, when I see these high-school students making it with their hot teachers, I'm more likely to think, "Lucky brat" than "What a monster," because I know if I was in their shoes, I'd probably be pretty damn eager.