Should schools allow the wearing of gang related shirts or colors?

Gangs have become an increasing alarm to our societies because they tempt young students to believe this fantasy of glory and power within this harsh social conflict. I strongly encourage uniforms in schools and discourage students to wear gang related shirts or colors because they're promoting violence and the fantasized "coolness" of wearing these shirts. It's almost as if wearing them creates emphasis on them and makes them feel more powerful. If a student is troubled and disagrees with wearing them then it must be that they promote it because someone who doesn't care about what their shirt reflects wouldn't care about not wearing them. Even if this was a freedom of expression argument, one must be aware that even in a nation where freedom of expression is a strong foundation one cannot state nor do as one pleases, there are boundaries in which to follow.