A legal challenge has been filed in the High Court on behalf of a 14-year-old girl excluded from a Cynon Valley school for wearing a Sikh bangle.
Sarika Singh refuses to remove her Kara bracelet
Sarika Singh has been excluded from Aberdare Girls' School since 5 November and will not be attending when classes start back next week after Christmas.
Campaign group, Liberty, has made the challenge, saying the school had breached race relations laws.
The school bans all jewellery and has said their policy ensures equality.
After filling the challenge, Liberty said the school has also breached human rights laws.
It says it also breaches a decision made by the House of Lords which allows Sikh children to wear items representing their faith, including turbans to school.
Liberty wants Sarika to be allowed to attend normal lessons at the school while wearing the Kara, and for the school to amend its uniform policy to comply with the Race Relations Act.
Sarika was excluded from her school three times last term and was taught in isolation for two months before that step was taken.
Aberdare Girls' School only allows ear studs and a wrist-watch
School governors rejected her request to wear the bangle after a "significant period of research" examining the uniform policy and human rights legislation in detail.
The school's governing body must lodge its defence in the High Court by 11 January and then the court will consider the case during the following week.
Anna Fairclough, from Liberty, said: "Sarika Singh has suffered humiliating isolation and is being denied a proper education simply because she wears the Kara, a small bangle worn by virtually all Sikhs both in and out of school and work.
"It is astonishing that the school continues to exclude her despite almost universal condemnation and 25-year-old House of Lords precedent." United Sikhs, an international advocacy charity, will also apply to file a third party intervention.
A spokeswoman for the Welsh Assembly Government has previously said school uniform policy was a matter for the governing body.
However, she said the government would shortly be issuing guidance on school uniform policy considering issues including health and safety as well as equality and discrimination.
More than 2,000 people have joined an online group in support of Sarika on the social networking site Facebook.