Catholic News Agency reports that Ms Playfoot, a pupil at the Millais School in Horsham, took her case to Britain's High Court on Friday, arguing that her school had violated her religious freedom.
She wears a ring as a sign of her commitment to abstinence until marriage. The ring is a thin silver band, engraved with New Testament verses encouraging Christians to be chaste.
The school prohibits all jewellery except for ear studs, but it does permit Sikhs to wear steel bracelets. The school said it would not make an exception for chastity rings because they do not form an integral part of the Christian faith.
According to the AP, Playfoot's lawyer, Paul Diamond, argued that secular authorities and institutions "cannot be arbiters of religious faith".
Speaking before the hearing, the girl's father, Philip, said the family's three-year fight highlights the growing secularisation of British society and the sidelining of Christian views and values.
Lydia's ring was inspired by an American abstinence-education program, called "The Silver Ring Thing." The program was launched in 1996 and received more than $1 million from the US government over 10 years.
Meanwhile in another story involving dress codes, Monsters and Critics reports that the Archdiocese of Manila has been distributing posters on what to wear in church since last week after many parishioners expressed dismay over inappropriate dressing during Sunday Mass.
"The guidelines are reminders to dress appropriately because other people are scandalised," Peachy Yamsuan, spokeswoman for the archdiocese, said.
Under the dress code, women should not wear short skirts, skimpy shorts, sleeveless blouses, tank tops or spaghetti-strap tops and plunging necklines in church, while men should avoid caps, shorts and basketball jerseys.
The archdiocese instead recommends that women wear blouses, corporate or office attire, school uniforms or long gowns, while men wear shirts, jeans or slacks.
Teenage girl takes chastity ring case to Britain's High Court (Catholic News Agency, 25/6/07)
Philippine Catholic Church archdiocese issues dress code for mass (Monsters and Critics, 25/6/07)
LINKS (not necessarily endorsed by Church Resources)
Silver Ring Thing
Purity ring (Wikipedia)
Archdiocese of Manila | Proper Attire in Church Posters
More dress, less promiscuity, says Perth Archbishop (CathNews, 13/11/06)
Perth schools take stand on ball season modesty (CathNews, 19/4/06)
Young Solomon Islanders in chastity push (CathNews, 30/7/03)
Vatican tourists told to maintain modesty during heatwave (CathNews, 18/7/03)
Pope tells youth to forget summer love, try chastity instead (CathNews, 9/7/03)