How would you rephrase this "with uniforms people cause less violent" like how would you put it as a longer sentence and more professional?
I'm not quite sure what you want it to say. Do you mean people act less violently when they are wearing uniforms? Do you mean that when people see uniforms, they act less violently? There is less violence when there are a lot of people wearing uniforms?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.