Clothes are distractions that keep individuals who can get "overly creative" noticed. The fewer distractions the better. If everyone looked fairly similar then it would be one less thing for students to be concerned about. There would be less jealousy, less insecurity, less envy, leaving room for more concentration on why you are really there, to listen read and concentrate on a lot of important information with good recall. There is too much focus on what people look like and not enough on what's Inside them. You do yourself a dis- service when you focus on what's going on around you rather than what you are there to learn.
The school dress code is important because it helps to encourage equality among the students and also to make sure that they get the same opportunity in the classroom. The dress code also reduces the chances of students getting robbed to and from school, due to easy identification. For reference, go to http://www.schoolsecurity.org/resources/uniforms.html.
All students have equal clothing or equal type clothing for two reasons. So that no student can 'out spend' others to be the 'most fashionable' or the most provocative dresser. And secondly, so NO student wear physically inappropriate clothing or sexually suggestive garments.
Well, I for one don't like to see kids (or adults) wandering around with bare midriffs, sagging and/or overly tight pants, or girls in skirts that are more like wide belts. Not that all kids dress that way; but too many do and a dress code would eliminate the "skuzz" effect.