Only had one fight in school. Got my azz whooped because I never saw it coming.
I was walking in the hallway between classes, when I was shoved down from behind. Next thing I rolled over and there was a kid on top of wailing away at my face. I was too disoriented to know what was happening until a teacher pulled him off. Luckily I was able to deflect most of his punches and had no injuries except for a few scratches where I had been knocked down.
He was set off because I asked him for my notebook back which I had let him borrow the day before.
School policy, even in those days, was to suspend both students. But I was on good terms with the dean, had a spotless record. They suspended him and sent me back to class. He didn't bother me anymore. But then, within a few weeks, I grew about 6 inches (good timing for a growth spurt I guess), and I think he was a little scared.
But man, I wish I'd seen him coming. I would have give him something to get upset about. I'd had a few scuffles outside of school hours (usually at the ballpark), and I always came out ahead.
When I was a kid, I was taught that I wouldn't get at trouble at home for sticking up for myself. Didn't mean I wanted to miss school though.
If you know your kid's teachers, and he/she gets suspended for defending him/herself, then it should be a simple matter to ask the teacher for "extra credit" to make up for any material they missed, especially if your kid is well-liked by the teachers. I think most policies don't allow teachers to give make-up work for suspensions, but they don't say anything about extra credit.