In my country private schools wear uniforms and public schools don't. It's all related to old elitist values at leasti s what I think
In my country, students from pre-school to university wear uniforms. I think uniform is required so that the students are distinguished which schools they are enrolled to. But in the university, there are some courses that dont require uniforms, like Engineering. Uniforms can also help because the students act and behave properly since they are wearing the school's pride and identity.