Luckily my children are not old enough for school yet. But they do go to playschool for a few hours three days a week. They have initiatives in place like a no biting policy, etc. that would help curb issues like bullying in the future. If a kid is too unruly or simply is not acclimating after intervention, guidance, and some time, they are asked to go to another "school."
But I did make sort of a rookie parent mistake. But I don't regret my approach for the time. At gymnastic yesterday the instructor had a play jungle gym section made out of mats. One boy apparently wanted to be in there all by himself and pushed my daughter out when she tried to enter (she will be two at the end of this month and he was a little older). I told her, "Push him back and then say you are sorry you had to do it!" The best approach in the world? No, but good enough for thinking in the moment and experiencing something like this for the first time. But no kid, boy or girl is going to push my baby around. If I didn't let that boy know he was not the "king" and the parent wasn't doing anything, I don't feel bad for having my daughter knock him down a peg or two and get his behavior to change (the boy was a little unruly during the whole session).