Would've been interesting if someone asked Serizawa why she's doing this, with her replying "because it's fun" as an echo to the idiots who forced her to give them head. Ain't payback a bitch?
Anyway, this chapter shows sensei is, in his own way, as trashy as the bullies - get buddy buddy with the ringleader's father because he's a big shot, and apply retarded logic to a serious issue at hand because it's more convenient that way.
I'm sorry I'm biased on this (personal reasons, I've been a victim of bullying for quite some time in elementary school), but I'm rooting for Serizawa here. Bullies deserve senseless deaths anyway.
That cliffhanger though....