I got in serious trouble in 3rd grade (early 90s) for having a snowball fight at recess. They had told us not to (something about ice chunks hiding in snowballs), but come on! We were little kids and there was a foot of snow on the field. What did they think was going to happen?

People are over protective of their kids. Yes, I know it hurts to see your kid scrape his knee, but he probably had a lot of fun doing it. It's a risk he takes playing tag (or whatever). Teach him how to identify risk and recognize when it's not worth it. Unless it's something that could kill or seriously injure them, show them how to do it safely.

I realize it's probably harder than I'm making it out to be (I don't have kids), but the amount of trust you have in your kid's judgement needs to increase with time or they'll never learn to trust themselves. My parents responded very well to my snowball incident. I got the "you broke the rule and the punishment is fair" kind of talk, but they didn't care that I got in a snowball fight. They trusted me to know not to throw ice at people and to leave if people started throwing it at me.

The world is a dangerous place, but there's a lot of situations that aren't nearly as dangerous as people pretend.