Okay while I do agree with some of your points, if you force mandatorty uniforms for all schools then you'll just be opening another can of worms, so to speak. While schools will no longer have to deal with such dress code violations that you listed, introducing uniforms will create a sense of elitism. Take Japan for example. In Japan your status in society is based on what school you go to (sad but true), so while you will eliminate, well I don't know exactly how to say it but sterotyping by appearance, people will instead be judged on what kind of school uniform they wear. And yeah I don't make much sense so ignore this if you want.

Oh one more thing, schools are too cheap to buy uniforms for everyone.