"Любимица учителя (учительницы)" is the equivalent of "teacher's pet," if I'm not mistaken.
You are not mistaken as such, the only thing is that it can be used in a positive way, too. The same goes for masculine version: любимец учителя. If you want a definitely derogative (in this context) form you use "любимчик", no matter is it a boy or a girl.