It's called being a kid. You get that shit out of your system early on and learn both not to be an asshole (because being an asshole gets you hit) and not to be a bitch (don't let people hit you or they're going to keep doing it).
As an adult you move beyond violence but the rules you learn will always be useful. Unwarranted aggression creates retaliation. Have friends to back you up. Back up your friends.
Kids are violent because they don't a better way yet.
People who are incapable of growing past violence is why we have police.
You seem a little simple, lad.