I love it; I wandered Westminster in battered trainers and am currently at my desk wearing a twelve year old t-shirt with a dragon on it.
One of the things we were taught at the (compulsory) diversity course was that there are lots of ways to discriminate.
A ruling against long hair, for example, could be a quiet way of discriminating against Sikhs. Refusal to accomodate part-time work or job sharing could be a way of discriminating against women or single parents. No jewellery? Well, there's a lot of religions that wear jewellery, even if it's not stricturally 'required' the way the Sikh bangle is. I've seen remarks like "there are plenty of other places for her to express her faith" and there are - at the moment. But if you tell a girl she can't wear what she feels is a religious symbol, on pain of expulsion, well, you've either thrown her out of the school, forcing her to find another, or you've forced her to give up what she views as part of her faith. Neither's good, and if more schools take up this uniform policy, where can she go? It's the kind of policy that leads to ghettoization - it was hugely damaging to the Sikh community in Britain, back when males had to cut their hair to find work.