They don't need to waste time doing that anyway.Kids are in school for one purpose and one purpose only: To learn. They need to dress in such a way as not to call attention to their manner of dress, as that is a distraction to learning. Teachers and administrators don't need to waste time figuring out what the latest gangland styles may be.
So what if they do dress to conform to the group? Some do and some don't, but that hardly calls for a system that makes that decision for them. Uniforms are designed for exactly what I said and they have always been used for such. This is in fact no different.Further, the argument that dress codes, or even uniforms, are against individuality are just so much hot air. Kids are, and will be individuals, after all regardless of their clothing. Moreover, teens dress not to be individuals, but to conform to whatever their peer group finds cool.