I don't think you're being overprotective BUT it doesn't have to be true for every kid to be needed for yours.
My sons worn a helmet since he was a toddler... Because he's FAST. Totally coordinated, is the only kid left standing (whenever there's a massive spill/jumble/gravity storm), etc.
But while most kids might get a bump, he's fast enough that IF he does run head first into something (1:1000) he splits his head open to the bone & nicks the bone. (True story). Which would be IMPOSSIBLE for the 10 kids all playing with him, because they were so much slower. They spilled all the time, at low speed, and were fine.
He almost never falls, but when he falls, he falls hard. He gets a helmet.
Your son sounds like he falls a lot. He gets a helmet.
Both kids are outside the norm.
And that's okay.
Its okay for our kids to need something different, without the system needing to change. Don't feel like you need to take on the world every time you notice something is needed for your son :) Just do what's needed for your son.
(( Obviously, we're not talking issues of fainting horror... Like recess on the street, unattended powertool play, etc.. OMG dangers aren't included in "Huh. Kiddo. Its time to get you a helmet." Or "Huh. I think you need to eat right before class." Its easy to fall into "All kids must wear Helmets!" Or "There shall be an extra snack for all kids before recess." VERY easy. So relax :). Go with your gut. Your kid needs something. Do it.))