It seems like a lot of fuss over not very much, and you wonder whether the school couldn't have saved itself some unnecessary bother by being just a bit more laid back about its uniform policy. And you can't help thinking that this is a case in which liberal-minded teachers might have been a tad influenced by their own beliefs. Would they have been quite so hostile if a pupil had come into school wearing a 'Make Poverty History' bracelet? As Shuggy said the other day about teachers calling for a ban on army recruitment in schools, even if it's true that most teachers are pacifists 'it isn't our job to make the pupils replicas of ourselves.'
The worst thing about cases like these is that they fuel a sense of victimhood among religious groups and feed their delusions about creeping secularism. Apparently the young woman in question is arguing that the ban breaches her right to express her religious beliefs under Article 9 of the Human Rights Act, and her father is quoted as saying: 'I think an important principle is at stake here, I think Christians should be respected for their views and beliefs' (see here and here on the question of faith groups demanding 'respect').
There's a genuine debate to be had, though, about the school as a secular space and how this should be expressed. In France, as the recent headscarf row demonstrated, the position is clear: it means a complete ban on all religious clothing and insignia. In the UK, with our policy of 'multi-faith' (rather than genuinely secular or faith-neutral) education, we're more confused. It appears that the school in this case 'allows Muslim and Sikh students to wear headscarves and religious bracelets'.
It needs to be one thing or the other: either allow the physical expression of any religious (or non-religious) belief, or ban the lot.