I think most if not all of western Europe as well as most other parts of the world do not have school uniforms and those students I have seen are usually dressed casually in jeans and tee Shirts etc.
The countries which do have uniforms seem to be those which are mostly English speaking ex colonies, Caribbean, India, Australia, NZ.p etc. Maybe Canada though not sure about that.
Communist countries always had school uniform which has maybe changed now, but Cuba, still communist, retains them.
I admired the impeccably dressed students in Jamaica years ago, in their pale blue uniforms which must have needed frequent washing though facilities to do it were so limited. They went fir half days with a different group going on the other half.
I am not against uniforms but I am against the particular design and high cost of some which don’t allow parents choice.