What is another reasoning for schools should not have school uniforms?

They take away our freedom. Wearing a uniform takes away our freedom of expression as it limits how we can express ourselves. They're uncomfortable. It can be uncomfortable for students and they may find it harder to concentrate.

school uniforms infringe upon students' right to express their individuality, have no positive effect on behavior and academic achievement, and emphasize the socioeconomic disparities they are intended to disguise.

Explanation:

One of the main arguments against wearing school uniforms is that students will lose their identity, individualism, and self-expression if they are made to wear the same clothes as everyone else. If this happens, then everyone will end up looking the same. It would seem bland and drab.