Two months ago, Lydia Playfoot, a teenager from West Sussex, took her school to the High Court over her right to wear a chastity ring.  Last month she lost.

Deputy High Court Judge Michael Supperstone QC rejected Miss Playfoot's case that she had been discriminated against, finding that Governors at Millais School in Horsham were entitled to insist she removed the ring.

Miss Playfoot, part of the Silver Ring Thing movement which promotes sexual abstinence among teenage girls, argued that refraining from sex outside marriage, as symbolised by the ring, was central to her religious faith:

As a Christian I do not agree with sex before marriage.  I believe I have a right not only to state my Christian views on sex, but also to demonstrate my Christian faith and commitment to God and my future husband not to have sex before marriage, through the wearing of a purity ring.

Preventing her doing so, not least when the school permitted Muslims girls to wear headscarves and Sikhs wear Kara bangles, amounted to discrimination, and contravened Article 9 of the European Convention on Human Rights, which secures for 'everyone... freedom of thought, conscience and religion... [and the right] to manifest his religion or belief, in worship, teaching, practice and observance.'

Miss Playfoot deserves respect.  Making such a public stand, not least when chastity is so unfashionable and those who espouse traditional sexual mores so widely mocked, demands a great deal of courage. Were more young people willing to make a similarly courageous and public commitment to chastity outside marriage, the sorry trend of destructive peer pressure, low self-esteem, sexually transmitted infections, teenage pregnancy, and abortion that Britain has experienced over recent decades might be reversed.

But being courageous is not the same thing as being right.

Although various newspapers reported the story in terms of religion, rights, discrimination, and political correctness, in reality, it was actually about categories, specifically the question: how do you categorise a silver ring?

Is it jewellery? If so, it seems odd that the school which permits students to wear ear studs should ban a student from wearing this particular piece of jewellery. What it symbolises is irrelevant. To discriminate between one piece of jewellery and another seems somewhat arbitrary, unless it constitutes a threat to 'public order, health or morals' (Article 9, European Convention on Human Rights) - which seems unlikely.

Alternatively, is it a symbol? If so, it is surely, in spite of Miss Playfoot's protestations, a 'moral' rather than a 'religious' one. The belief that marriage offers the only suitable context for sex may be part of traditional Christianity, but is an ethical outworking of basic doctrine, rather than an essential article of faith, still less an essential article that requires symbolic expression. Many chaste, young Christians do not wear silver rings. Conversely, many young non-Christians hold similar views on chastity. Miss Playfoot's moral stance may be commendable and her silver ring may be an important part of it, but it is not a necessary or essential part.

If this is so, the school is surely right to ban it.  Not doing so would preclude it from drawing too many other moral lines. If Miss Playfoot's beliefs regarding sexual abstinence entitle her to wear a silver ring, do mine (regarding the poor) entitle me to wear a Make Poverty History bracelet, or my friend's (to abortion) to wear a pro-choice pendant? The fact that someone's moral stance is founded on religious beliefs is irrelevant.  If a school prohibits the wearing of moral symbols, there is no place for a silver ring.

What, then, of her Sikh and Muslim peers? A Kara bracelet is one of the five symbols of faith, known as Kakaars, which include Kesh (uncut hair), Kanga (comb), Kirpan (sword) and Kachehra (a special type of shorts). It is thus more important, arguably essential, to the Sikh faith than a silver ring is to orthodox Christianity.

And headscarves? There has, of course, been much debate over recent years about the significance and importance of these to Muslim women and girls, but the opinion, at least of Miss Playfoot's school, appears to be that headscarves, if not the full hijab, are intrinsic to the Islamic faith in the way that silver rings are not the Christian. Doubtless, however, someone somewhere will test this conclusion at some point.

The complexities of this case - not least the exception made for ear studs - make it easy to see why Miss Playfoot should feel resentful at the adjudication. Yet, despite that, the judge’s decision is the right one.

And yet, one cannot help but wish to see many more Lydia Playfoots - although preferably in the playgrounds rather than the courts.

Nick Spencer is Director of Studies at Theos.