When all of the students in a school are required to wear uniforms, intruders stand out from the crowd. It's much easier for school officials to spot people who don't belong on campus when they aren't in uniform. This creates a safer environment for students and faculty members. Students are also unable to wear gang colors or symbols, so fights brought on by those issues are avoided.
School uniforms help reduce cliques that can be easily formed by the way students dress. If everyone is wearing the same thing, students cannot use clothing to stereotype and judge each other. Uniforms make students look much more polished, setting the tone for a more professional learning environment. They can also help to give students a sense of pride and unity, which prods many to work harder to succeed in school.
When students are forced to wear uniforms to school, they are unable to express their individuality. This is unfair to them, as they are all unique individuals who exhibit parts of their personalities through their clothing choices. If students are not able to use their clothing as an outlet to express themselves, they may turn to other more dangerous behaviors, such as starting fights or experimenting with drugs and alcohol as a release.
Every student is build differently. Therefore, what is comfortable and flattering on one person might not be the same to the next. If students are forced to wear clothing that is uncomfortable, they are going to be less focused on their studies. They will also be made to feel self-conscious and uncomfortable if they feel the uniforms do not look good on them. There are thousands of clothing brands available because there are so many different definitions of comfort. School uniforms do not account for this.