[Sangetsu]

The students at my school wear uniforms. They are not permitted to dye their hair, wear makeup, or jewelry, other than a wristwatch. The school's idea is that students should spend their time before and during school thinking about their studies, and not about their clothes. In school, the priority is getting an education, not making fashion statements (or other types of statements).

I agree with this policy, it is used because it works.