Schools always did this.

Never expelling the bullies, always expelling the kid that was bullied to their breaking point when they retaliated.

I am convinced that the people who choose to be teachers (and especially principals) also tend to be the kind of people who like and relate to bullies.

In general a lot of them seen to enjoy bullying as a method of "correcting" other people to align with your will. A method some of them seem to feel they are unjustly restrained from utilizing fully.