I just cannot understand what the problem is. Apart from school policies which are blatantly unclear, I cannot comprehend why any parent would ever send their child to school in any way which even possibly does not comply with the uniform and appearance rules.
I have read of only one case in the past few years where the school seems to be in the wrong: a case of a boy whose shoes looked identical to the allowed shoes in the uniform guidelines provided by the school (they had photos). In every other case, including all those sadfaces in the DM, on the news, the story this week with a mother and her child with a coloured Kickers logo moaning "but these cost me £50, they're not against the rules" (the guidelines state clearly no coloured logos), and in this thread, it is blatantly obvious that the child and parents are at fault and there is a clear violation.
For this one sphere in their life, for this one period in their life, teach them respect, teach them right from wrong, regard education as a rounded experience and not just about passing Maths, teach them awareness of others and how sometimes the group adapts to care for all, that you don't always get what you want and demand, that the world does not revolve round them, to just wear the uniform, belong, be proud, concentrate on their studies, and treasure these hours in school to forget about fashion and focus their wonderful minds on learning. Support the schools, do your job as parents, educate your children.