Exactly my experience as well. Fighting back is the only thing that ever made the bullying stop. I fought back once in the locker room against a boy two years and two feet older and taller than me, basically lost the fight immediately, but because I fought and wouldn't submit, everybody else stopped the fight and after that day I was never bullied in school again.
The reason I never fought back sooner is because I was scared of the rules even more than the bullies. The "Zero tolerance" rules made clear that if I fought back I would be just as bad as the bullies, and in just as much trouble (except I'd actually be in more trouble, because my parents would be livid at me for getting suspended while the bullies' parents wouldn't give a shit.) "Zero tolerance" means zero due process. It's the school administrators essentially siding with bullies by default because it makes the paperwork easier. Absolutely immoral. It should be their responsibility to figure out who actually started the fight and punish the perpetrator but not the victim.
In the end I didn't get in trouble after all, because locker room fights were beyond the eyes of adults and nobody ratted anybody out. I resent the teachers and the administration the most, for making me afraid to stick up for myself. The kids who bullied me were psychos or broken people, and I find it easy to forgive them. But the administration did harm to me by being lazy bureaucrats.