Chastity ring banned at English school

The first news item I heard when I got in the car this morning was a story on a girl who was banned from wearing her chastity ring at a Millais School in Great Britain. Lydia Playfoot, who attends a "non-denominational religious secondary school for girls," was forbidden to wear her ring on the grounds of the school's anti-jewelry policy that also forbids crosses and crucifixes from being worn. The same school allows Muslim girls to wear their religious garb, including bracelets.

Two things:
1) What is a non-denominational religious school? Judging by the variety of religions that attend, it seems like a secular school to me. I went to the school's Web site and could only find one place that mentions religion: The religious education department, which has four symbols on its page (among them a cross, a Star of David, a crescent moon for Islam). The department's mission statement: "The R.E. Department at Millais School aims to provided [sic] an environment which fosters genuine, non-denominational enquiry into the place of Religion in society"

2) Does this seem like anti-Christian bias, or were the school officials just being consistent?