Every public school I attended had a rule against "distracting" hairstyles. It seemed to be up to the administrators to decide what constituted a distraction on a case-by-case basis. Pretty much it just boiled down to the fact that if the hairstyle caused disruption in class or posed a danger (in for example shop class, mechanics or home ec) then it had to be modified. There was a kid in middle school with a foot-high blue mohawk, so obviously the public schools can't enforce the rule too much. I also remember a ton of boys with long hair but that was in older grades, not so much elementary school. I'm not talking touching the collar long, or just shaggy, I'm talking halfway down the back or longer.