I gotta say, that unless it's a school with uniforms, this is wrong. In the three high schools that I went to (deep south U.S.), the general policies were that your hair couldn't be a "distraction to other students". Even then they rarely did anything about it. Once a kid was moved to the back of the class because the hair was piled so high it was hard to see around it (B52 style), and one other, a guys afro (popular in the 1970's) was HUGE, and he put several picks, little green army men etc as a joke. He was moved over to the window where he was out of line of sight to the teacher.
If hair length is what triggers the school board, they have much larger issues that need to be addressed.
If hair length is what triggers the school board, they have much larger issues that need to be addressed.

