The official position on WHY uniforms are required by our parish school is this:
1) Uniforms give children a sense of pride in their education, which is exemplified by their respectful attitude toward their schoolwork, their teachers, fellow students and the facilities themselves. It has been proven in various studies that schools that employ uniforms have higher student achievement and fewer discipline problems.
2) By putting on a uniform, it is a psychological cue for the students to ready themselves for learning.
3) Uniforms are the first, easiest step of discipline, including self-discipline.
4) Uniforms "even out" any disparity in students in terms of economic status or ethnic differences.
5) As a parent, I would add that uniforms not only save parents money but remove the whole "what to wear" headache when getting the kids up for school in the morning.
6) Uniforms do not prevent children from expressing their individuality, but refocus kids to expressing their individuality through their essays, creative writing, artwork, music, etc., which is a more beneficial way of teaching them how to express themselves.
I would be curious to know why you are against school uniforms. I was, too, until I had personal experience with them.