The High Court on Monday upheld a ban on a teenager from wearing a so-called "purity ring" at school to signal her refusal of sex before marriage.
Lydia Playfoot, 16, said she was "disappointed" by the ruling in central London.
Her school, the Millais School in Horsham, West Sussex, denies infringing her human rights, saying that the ring is not an integral part of the Christian faith and violates its uniform policy.
"As a Christian I do not agree with sex before marriage," Playfoot said, adding that she was "very disappointed by the decision ... not to allow me to wear my purity ring to school as an expression of my Christian faith.
"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."
The teenager's legal action is the latest instalment in a long-running debate in Britain over the right to wear religious clothing or symbols in public.
The father of a 12-year-old girl fought and lost at the same court earlier this year for the right of his daughter to wear the full-face Muslim veil or niqab at her school.
Playfoot is part of a US-based programme -- "Silver Ring Thing" -- in which young people wear a ring engraved with a Biblical verse to show their decision to abstain from sex before marriage.
Playfoot's father, Phil, a pastor at Kings Church in Horsham, insisted his daughter was not living out his wishes or beliefs, adding that "it's something she wants to do for herself."
Phil Playfoot and his wife Heather are part of a group of volunteers that run the British branch of "Silver Ring Thing", which claims that 25,000 youngsters have committed to abstinence from sex before marriage.