I hate hate hate hate hat school uniform - especially on primary aged children
it is not a leveller - you can see who has uniform from a supermarket, hand me downs worn out etc and those who buy Next, M&S etc.
You can see who is wearing shoe zone shoes and who has Kickers, who has an adidas bag, who has Vans and who has Primark. You can tell by coats, hair cut and lunch boxes - it is not a leveller
It is as easy to tell the haves from the have nots
People talk of the fashion parade, the difficulty choosing what to wear on non-uniform days but that is because it is a special day - aa day for kids to show some personality once or twice a year, it is important to them, they want to make an impression and be seen for who they are as they never normally get the opportunity. As others have pointed out - it is not an issue when kids can wear what they want - they settle in to it and it is fine.
DS goes to a non-uniform school - his rules are - practical, nothing torn or revealing, nothing with swearing and nothing that could be used as a weapon. He wears jeans, t-shirt and a jumper every day - no hassle - most of his t-shirts are from a multipack from Next. His clothes are more hardwearing than uniform and made from nicer more natural fabrics.
I find it far less hassle because he can wear anything that is there and clean. He is much happier because he wears what makes him feel comfortable.... and it has had no impact on his academic achievements.