Rhondda Cynon Taf Council said this week it would not be able to provide "any support or financial assistance" to the governing body of Aberdare Girls' School if the case goes ahead at the High Court.
Human rights group Liberty filed a legal challenge in the High Court in December, arguing the school governing body had breached race and equality laws, as well as the Human Rights Act, by not allowing 14-year-old Sarika Watkins-Singh to wear a religious bangle, called a Kara, to school.
She was excluded for refusing to remove the steel bracelet, which the school said was against its code of conduct on jewellery.
The case was waiting to be considered by a High Court judge as TES Cymru went to press, along with Liberty's request for Miss Watkins-Singh to be allowed to return to school.
Clearer national guidance on school uniform is expected to be issued by the Assembly government today as a consequence of the case, which has received global interest.