Not really 'zero-tolerance' but close to it. I was just a normal student at my elementary school while the bully had a very wealthy father that donated a lot to the school (it was a private school). These donations lead to a lot of leniency for his actions and he was quite a violent person.
I remember one day I was walking back to class after recess holding a soccer ball and completely out of the blue I got tripped backwards on cobblestone and smacked the back of my head so hard I couldn't walk properly for a few minutes. I don't remember much of the actual day beyond that though what I did remember was how mad I was that no punishment was given for the bully and we were both warned that if something like this happened again we'd be suspended.
That one was pretty bad though to go even further the bully had a younger brother that I guess had been briefed on his brother's hatred for me, so just randomly while walking across the field he went absolutely ballistic on me and knowing how no punishment was given out last time and also how the principle told me if I got in any more trouble I'd be suspended I just let the kid go to town for what felt like quite a long time. Eventually he finished and I was there all bloody and got hauled off the principal's office.
The principle then proceeded to act as if the fight was actually a fight and not just blatant assault on someone who didn't even defend himself. When he started talking about a one-day suspension at most for the kid I fucking lost it on the principal who after me literally screaming at him in tears decided to settle for a one-day suspension for the kid and another warning for me.
I may have been a complete wimp at the time as I was a shy kid who liked video games rather than sports though my dad was a complete badass. After that day I told my dad what had been going on and he was fuming and was going to take the next morning off work to sort things out. However the bully's dad beat him to the punch by calling our house and demanding I apologize to his son for getting him suspended.
When this happened my dad doled out the most brutal verbal smackdown I had ever witnessed, I remember smiling ear to ear listening to him take the bully's dad down every possible peg and turned it around so his dad forced his kids to apologize to me instead. I gained so much respect for my dad that day and those two fucks never tried to mess with me again.