That's a difficult question. In my opinion dress codes are not important. I think pupils should wear what they want at school. If people don't like their clothes, they won't be happy and I think that's the point. 
But on the other side dress codes are a good idea to help pupils not to spend the whole money on clothes or other expensive 'fashion accessories'. The young people should learn to handle money and so the 'military look' is maybe a good suggestion.
I think all in all dress codes are not necessary but they can be a help for teenagers to learn to handle money.
