Kids should be able to wear their own style, school appropriate of course.
As Kids Get Older
As kids get older they start to develop their own taste in clothes and style. Keeping kids from expressing themselves can lead to negative affects.
If a kid is told what to wear everyday, then there is no need for school shopping. School shopping for clothes is one of the best parts before school. You get to buy all sorts of shirts and jeans with all different types of designs that describe you and your personality.
Clothes affect behavior
When someone is wearing a bright shirt they are usually really happy and when someone is wearing nothing but black they are usually sad. The choice in color and design in clothes usually describes the student.
Kids who wear the same style usual end up being good friends. They then find out they find out they have a lot in common and become even better friends. If all students were to wear school uniforms you wouldn't be able to see who your future true friends could be.