I've grown up in countries where school uniforms are incredibly rare, and have therefore never worn one. This means that to me, the mere idea of school uniform seems incredibly antiquated, militant and stuffy, and I have a really hard time seeing a positive. Since kids need clothes for when they get home, it seems to me they just end up getting MORE clothes, rather than it saving any sort of money.
Picking up my friend's kids from school, you could still always tell who came from the better off families...rucksacks, jackets, hair accessories, shoes, state of uniform, state of hair, state of person picking up the person become the tell-tale signs and the "important" factors for the kids instead of the clothes. They'll always find a way of making the unwary feel left out, whether that's the way your shoe-laces are tied or the pencil case you use.