I had a school uniform at secondary school in the UK, and it was just an accepted part of the deal. I found that it was a leveller, or maybe I was just not so observant, and it did not worry me that one girl wore a uniform that was in better condition that anothers. When we were allowed to wear "a suitable top" with our school skirt in the 6th form, then you would see a more marked change between the girls in the quality of the clothes they wore. With todays insistance on labels and designer gear, that would be even worse. No one remarked on it then, 1964-1970, as they do today.
After I left, the uniform changed, and the rule seemed to be simply wear a blue blouse navy skirt, and navy cardigan, but there were no rules about the style. It wasn't uniform in any sense of the word. Now it has been changed to blue blouses with navy trousers, or skirts, and a sweat shirt with the school badge and the girls look very nice.
My main beef with school uniforms is the colours some schools wear. Unless there is a second hand garment going via schemes run by the school ( and they did not exist in my day) few places other than the official school outifitters sell blazers in scarlet, royal blue or green. A friends son wore a bright green blazer for the first 5 years of his school career, then the 6th formers wore black blazers. By the end of the 5th year the green blazer was very worn, but friend made her lad nurse it along until she could buy him an M&S blazer for much less than the cost of the school outfitters.
You can express creativity in other ways than dress. And besides, without things like school unifrom, what have you got to rebel against?
At an old girls reunion I met a lady who was at school in the 1950s. Her mother bought a blouse from the school outfitters, and the assistant recommended one with room for growth. She said it had so much room that she wore it as a maternity smock when she was pregnant with her son.