Sex romps? The term is rape.
RAPE
Yes, what she did was totally wrong and disgusting, and the fact that the boy was was underage makes it even worse.
But here's the thing about calling it "rape":
Firstly, it is insulting and demeaning to true (pre-pubescent) child rape victims to place a sexually-active 15-year-old in the same category as them.
Secondly, it implies that if the boy were 18 (and not her student), then it would be OK for them to have sex.
And lastly, as disgusting as it is for a woman to pressure and use a man sexually, you can't really compare it to violent male-on-female rape. The latter, I assume, is far more traumarizing for the victim.