My school was always pretty good with fights.
I got in quite a few fights, but was never suspended. The people who started the fights (who by the way, for the most part, were obvious trouble-makers in and outside of classes) got in trouble. Whether that was detentions or suspensions, or even expulsion.
Minor fights between good students, people who clearly aren't trouble makers, usually ended with both of them getting a detention.
If the fight went to the extreme and someone was grossly beaten up, then they'd be expelled, no questions about it.
Often the parents of the child beaten up would also press charges.
There has never been a case at my schools where by someone defends themselves and gets in trouble.
Fights were always pretty obviously started by either one person, or mutually started by both sides.