The Columbine incident ties into this debate, but only loosely. Most of the districts contemplating school uniforms are attempting to address gang-related crimes. The reasoning behind school uniform initiatives seems to be two-fold. One line of thought seems to be that by eliminating the ability of gang members to dress like gang members a gang's ability to operate will be hampered. But this probably doesn't give enough credit to the ingenuity of human beings.
Prisons have pretty severe uniforms and a huge gang problem.
A second line of thought seems to be that by adopting uniforms, non-gang members will be in less danger of accidentally wearing the wrong piece of clothing and incurring the anger of a gang. This argument has some merit. A third argument in favor of uniforms is economic. These days, parents may save some money on school clothes if they can buy a couple of bland uniforms rather than a wardrobe full of this year's popular designs. A fourth argument is that uniforms remove one more distraction from the classroom.