Sarika Singh, 14, the only Sikh girl at Aberdare Girls School in South Wales, has been suspended for the second time for refusing to take off her 'kara'.
The school said the bangle broke its code of conduct. Pupils are allowed to wear only a wrist watch and one pair of plain metal stud earrings. It added that the rules had been in place for many years and had been set up to ensure equality.
Sarika's mother Sanita Singh, 38, has taken legal advice and plans to challenge the school's decision. Singh, her daughter, and a representative from the Valleys Race Equality Council, a self-styled charitable voluntary organisation, attended a meeting at the school on Tuesday with head teacher Jane Rosser.
Wayne Lee, a spokesman for the council, confirmed that the pupil had been excluded from school again.
"Sarika is very upset and wants to go back to school. She is a good student and she wants to see her friends like any other 14-year-old."
Pending the outcome of an appeal, Sarika was taken out of her classes and taught separately for nine weeks. She was excluded this month when she continued to ignore the ban.
Sarika, from Aberdare, said, "It is very important for me to wear the 'kara' because it is a symbol of my faith and a constant reminder that I should only do good work, and never do anything bad, with my hands."
But the governors rejected her request to wear the bangle after examining the uniform policy and human rights legislation. The school said it would not comment until it had told Singh of the latest suspension in writing.
Liberty, the human rights group, which provides legal representation for Singh, said the law lords had ruled that Sikh pupils could wear items representing their faith, including a turban.
Anna Fairclough, Liberty's legal officer, said, "Legal precedents established 25 years ago make clear she should be allowed to wear the 'kara'." She added, "The school's reaction to our client's desire to modestly observe her faith has not only been discriminatory but defies common sense.
"Our proud tradition of religious freedom must be upheld for Singh. Unfortunately, the school's uniform policy appears to mean that no Sikh can attend the school without compromising their beliefs."
A spokesman for the Welsh Assembly said rules on uniform were a matter for schools' governing bodies, but issues such as equality and health and safety should be considered.
The spokesman added, "Whether a school uniform policy breaches the Race Relations Act 1976 is a matter for the courts."
The Valleys Race Equality Council, whose director is Ron Davies, the former Welsh Secretary, said, "The school needs to take fresh advice. They seem to think that if you treat everyone the same, that is the end of the story."
"But the whole basis of equality legislation is that people may have to be treated differently because of who they are. You don't tell a one-legged man to join the queue."
Cynon Valley Labour AM Christine Chapman commented, "I believe the school should be more flexible. I am aware that schools in Birmingham and Cardiff allow Sikh pupils to wear the 'kara' bangle, and that it is not an issue. I am very concerned that Sarika's education is being affected by this dispute and want it resolved quickly."