As a child I went to lots of schools (10 in all) and although most were state funded, on only one occasion can I ever remember being aware of the relative wealth of child and beyond realising that this girl had free meals, I didn't really think about it and I can never remember the relative poverty or wealth of families ever being something that we children ever talked about or noticed.
As for uniforms, I wore them and like most children in school uniform I made a habit of subverting their purpose, hitching my skirts up, or in my particular case, having lots of visible repairs. I was an army brat and at 11 went to boarding school, we had a strange head teacher always preaching about to monetary sacrifices our parents made for us, which was ridiculous, as most of us were army brats and the Minstry of Defence paid our fees. Anyway, I made a habit of making it clear that my uniform had lots of repairs because I was conscious of the sacrifices my parents were making. It really irritated the head teacher, which was my aim.
At my children's primary school they did not have uniform, but they had rules. It was the 1970s and trainers, jeans and T shirts with pictures or slogans were banned.
As children grow up and leave school, they need to learn that in the adult world, you need to know how to dress for the occasion. Different jobs require different clothes and the same applies away from work. The best way to learn this is by understanding what are appropriate clothes for school and not just mindlessly putting on a uniform and then subverting it.
I cannot remember at any school I went to, nor any my children went to where any other than a very few, took pride in their uniform. Most hated being labeled by their uniform, advertising which school they went to and took it off the moment they got home.
As for being 'good' for children. If children get labelled for being poor or whatever, the fault lies withtheir arents who brought them up to think poor people should be sneered at.