Maybe the rebbeim then were too emotionally weak to not hit. That surge of violence is the result of Hitler and the holocaust, and thank goodness the effect has started to wear off.
I used to listen to the horror stories from somewhat older relatives - and they were sickening. I myself wasn't hit as often by rebbeim but the few times were more than enough.
Your making it sound horrible. IME a loving rebbe giving the appropriate slap, was a normal healthy part of school. Just like being sent to the principles office. Or writing out 500 times: I won't talk in class (-is that to much today also?).
I don't know your story, but from the kids I grew up with, I don't think that we were negatively affected at all.