Uniforms are reducing violence by percentages that are higher than 80% which is a lot compared to the violence that still happens today to schools that don't have school uniforms. The research shows that violence can lower by school uniforms. If more schools have uniforms it can lower bullying and violence in schools.
School uniforms also prevent students from concealing weapons under baggy clothing,  make it easier to keep track of students on field trips, and make intruders on campus more visible. Frank Quatrone, superintendent in the Lodi district of New Jersey, stated that "When you have students dressed alike, you make them safer. If someone were to come into a building, the intruder could easily be recognized."
Introducing school uniforms could reduce crime and violence at schools. This is because of the fact that school uniforms and their wearers have been studied. School uniform wearers have been shown to be more obedient, and these people also cannot wear certain gang-affiliated clothing that would incite crime and violence.
Yes, introducing school uniforms can reduce crime and violence at school, because it levels the playing field among students. There will not be students displaying gang colors or symbols through clothing. Students who cannot afford fancy clothes will not feel inferior. Students can take pride in being members of their school by wearing the uniform.
I believe implementing school uniform policies can reduce crime and violence at schools. Teenagers can be judgmental of each other and often spend time comparing each other in all facets of life. Some of this can be stripped away by mandating school uniforms which require students to essentially dress the same.
Uniforms could prevent gang colors and symbols, as well as offensive content, from being displayed. People would be less inclined to pick on someone from a lower income group, and females (and males) would be better covered and protected from others that may sexually harass them based on what they are wearing.
Introducing uniforms to reduce violence will not work. Sure it may allow people to be slightly more confident, and not afraid because everyone is dressed the same but, that does not reduce the chance someone will have the thoughts to harm someone outside of school or inside because of who they are. If the cause of violence is because of the style or choice of clothing then when the children are allowed to face life on their own, and because they couldn't deal with the fact someone dressed a certain way, the violence will rise outside of school, and into their adult if they can't handle the differences.
This is one of those things that Americans love to bring up without any basis in fact. But let's look at the British school system, where uniforms are the cultural norm. Kids there are still getting into trouble, still committing crimes, and still bullying their classmates. The uniform isn't going to stop children from being cruel.
What could possibly be gained from introducing mandatory school uniforms that would prevent violence? Violence is not an issue about expression or fashion, violence is a mental health issue, a bullying issue, an issue with the way our social environment has become. Making everyone uniform is not going to stop that - postal workers wear uniforms, don't they?
Kids can still commit crimes and be violent even when they are wearing school uniforms. Students will still find things to fight over and reasons to hate each other. There will still be things to steal or damage. Changes in policies and more effective punishments for violations might be better solutions. More staff who are better trained to deal with the students would also be helpful.
It is unlikely that school uniforms will reduce crime and violence in schools, for the following reasons. First, there is no evidence that crime and violence in schools is the result of diverse clothing. While it is true that there is the occasional "expensive sneaker robbery" crime, there is no evidence that this is a primary motivation for crime or violence. Second, requiring young people to wear uniforms is unlikely to curb their violent instincts (assuming they have such instincts). Rather, it appears more likely to make them angry. Finally, most families will only be able to afford one or two uniforms, which means that students will often go to school in un-laundered uniforms, which will cause classrooms to stink and likely lead to more (not less) violence.