Having all students in the same clothing takes some of the socio-economic cues from fashion out of the equation.
Schools bring students together from a variety of socio-economic backgrounds. This is both a positive, as it exposes children to diversity and builds ethnic, religious, and socio-economic bridges, but it can also lead to students being singled out and bullied for their economic standing.
With all students dressed the same way, teasing of students who might dress differently to others (either through choice or due to economic reasons) is minimised. In a survey among teachers, 83% thought that the adoption of a school uniform could prevent bullying Aside from minimising bullying for socio-economic reasons, school uniforms also create a level playing field of expectations. Evidence suggests that when students are wearing nicer clothes, teachers have higher expectations of those students. This can lead to teachers paying extra attention and spending more time with those students while neglecting those who appear more unkempt. School uniforms create a level playing field both among students and teachers.
This is untrue. Anyone who has been to school or taught in a school will know that a uniform is unable to conceal socio-economic differences. More affluent families have new uniforms instead of second-hand ones. They replace uniforms when they become dishevelled instead of wearing them until they tear. Poorer students' uniforms are more likely to be poorly-fitted. Nor can uniforms effectively curb bullying. Bullying in schools, as in wider society, is the result of deep power imbalances that go far beyond what clothes a student is wearing. While uniforms may reduce bullying along lines of clothing, they will do nothing to tackle the root causes of the problem and will merely push the bullying to other avenues of attack and victimisation.  Most teachers will tell you that bullies will still bully victims even when there is a uniform policy. The nature of the bullying will merely shift to the way the victim styles their hair or does their makeup, or what bag they carry and shoes they wear.
[P1] School uniforms create a level playing field. [P2] They should be mandatory to avoid inequality.
[Rejecting P1] School uniforms do not create a level playing field.