Earlier this year, I got into a fight with a kid during detention (har, the irony) because he kept kicking me under the table and even though I told the teacher, she just replied, "Deal with it". He kept it up and I promptly ended up telling him to fuck off, at which point the dude went into RAEGMODE, and he leaned across the table and tried to punch me- I pulled back and stood up, and he reached back, grabbed his chair (one of those light, plastic ones) and threw it at me. While the teacher obviously saw, she didn't do anything or even say anything until I rammed the table into him, knocking him on the floor, at which point the teacher broke us up. He ended up with a week of suspension for "use of a potentially deadly weapon", and I got two days for a "viscous attack on a fellow student". I asked the teacher and principal both why I was getting in trouble when he not only started it, but also because the teacher had failed to do anything after I complained about his behavior, or why she didn't do anything after he threw a damn chair at me. The bigger question is, why wasn't this kid on anti-psychosis drugs or at least Ritalin, for God's sake? He obviously has some issues going on if "fuck off" justifies hurling a chair in his mind.
I was seriously disgusted, not only by the teacher's lazy reaction before the fight and her reaction during the fight, but by the fact that the school board would let a kid like that be in normal classes. He had quite a record- I heard the guidance counselor saying, "This is the fourth time for this school year! Don't you have any self-control? Most kids don't get into four fights over their whole 12 years in school!" He obviously can't control himself, so I don't fully blame him for this- I believe the school board is more at fault. They have lax policies on restrictions and extreme punishments that they hand out like candy, even if the student doesn't deserve it. The only security we have at my whole school is a single police officer, with no metal detectors or anything around the perimeter- every student could show up with a handgun concealed up their ass and none of the teachers would notice.
tl;dr - Schools do virtually nothing to prevent fights, and they give out harsh punishments to the participants. Even if you don't fight back, you might still be suspended because another child chooses to hit you without reason! The story that they're just "trying to follow policy" is cock and bull; they're just lazy and try to balance out their lack of preemptive restrictions with harsh punishments that make it seem like they're actually doing something.