Interesting parallel with the recent cases of the pupil being excluded for wearing a ring, and the employee being told not to wear religious symbols publicly at work. To me, it has nothing to do with religion. It's a case of "The condition for attenting institution X is [dress code] Y. Do Y or go elsewhere." The individual has the freedom to express Y. They do not have the freedom to force Y upon situation X, whether X be a job, a school or any other private institution.
It's a balance between the freedom of the institution and the freedom of the individual. An institution is made up of a number of individuals, so who is to say that the one individual may overrule the many? Is this another left/right wing divide?
As with all my views, this may be changed by any reasonable argument.