Uniforms give poor kids a chance to excel at social skills at a young age. A lack of uniforms allows all the children in the school to realize who the underprivileged kids are. This leads to bullying and causing these kids to feel unequal. Equality is important in child development.
Uniforms can be good when students do not have to worry about what to wear and how to compete with each other. They can also be good for showing solidarity and position. But sometimes they can be used to intimidate others, such as when soldiers and police wear them. Depending on intention, that can be good or bad.
It's just another thing for teachers to police and they are overworked as it is. In the UK every school has a school uniform that is enforced rigorously some places will give you a Saturday detention for a small transgression like a red trim on your sock cuffs I mean hell it's not like anyone actually sees much of your socks why would it matter.
Everyone hates them and it is especially annoying when you finally grow out of them like week before you leave and finish your exams which you have to wear the uniform for.
While I agree a stranded needs to be maintained a uniform is not the way to do it it breeds an us and them mentality between the students and teachers a dress code would be preferable as you could A) dress weather appropriate so you don't get too hot or too cold which would distract you
B) actually be comfortable and learn how to dress appropriately for the enviroment