It's not a communist thing, communism is an economic political philosophy..
It's more about equality, which you seem to have something against... I'm not sure why. No one is better than no one else. We're all in this together, this life, this human struggle, united as brothers and sisters. Well, i think so anyway.
Imagine if you were poor and couldn't afford good clothes and everyone else was wearing designer labels, would you feel great? Would other people tease you?
It's also more about identifying, yes you are indeed a student here, it makes that aspect a lot easier.
Its also about solidarity and cohesion as well, if everyone has the same uniform it really helps that along, its one of the reasons (albeit a smaller one) that the various armed forces have a uniform.
School students shouldn't have to worry about clothes or looking fashionable every day, they should just focus on their work instead of silly things like that. (They can do things like that in uni if they wanted to anyway)
Just my 2c. (I know i bumped the thread but i couldn't help myself)