The debate about religious dress is often at its sharpest in schools where personal and religious choice conflicts with uniform policies intended to eliminate difference and promote social integration.

Muslim classroom assistant suspended for wearing a veil

""Increasingly bitter debate" about that school assistant

Last year, a British teenager took her school to court

And then there's this, the story I was remembering this morning and which I argue doesn't make it ANY better for being broader or politically cutting the other way:
Students barred from wearing Christian chastity symbol in UK school

And this comment seems to fit here:

It doesn't matter to me whether it's an expression of faith or not. The way I see it, religious freedom is simply a sub-category of freedom of speech/expression, and it is this higher freedom that is really of more concern to me. So a school should have no business saying that ONLY jewelry with a religious significance can be worn; this is discrimination against the non-religious, and it places religious freedom over all other freedoms.
But even if they have this rule, they should apply it consistently to all religions, and it's not their business to pick and choose which items they think are legitimate expressions of faith and which aren't (this strikes me as extremely arrogant).
God: proof that imaginary friends are not just for children.