The court heard that the steel bangle worn by Sikhs, including cricketer Panesar, was a symbol of faith, not a piece of jewellery, and the school had breached Sarika Watkins-Singh's human rights by banning her from wearing it.
The 14-year-old is appealing against the decision by Aberdare Girls' School in South Wales to refuse to exempt her from the strict uniform policy, which bans the wearing of religious symbols.
When Sarika would not remove the bangle, known as a Kara, she was taught "in educational and social segregation during school hours" for some months before being excluded for a day, then for five days and finally indefinitely, said her lawyer Helen Mountfield.
The judge, Mr Justice Silber, must decide whether the school's policy amounted to unlawful discrimination under the 1976 Race Relations Act, the freedom of religion provisions of the 2006 Equality Act and the 1998 Human Rights Act.
Ms Mountfield showed the judge a picture of Panesar wearing the bangle when he asked to see what a Kara was.She told him the Kara was one of the five Ks of Sikhism, and worn by more Sikhs than the turban, which is not one of the Ks.
She cited a House of Lords decision 25 years ago, which had never been questioned, that a Sikh boy was subjected to indirect race discrimination when he was told he could only attend a school if he cut his hair and ceased wearing a turban.
She said: "There is no string of authority to say that school uniform rules may trump religious dress codes".
Mr Justice Silber commented that the only issue of fact in the case seemed to be whether Sarika was actually obliged by her religion to wear the Kara.
In February, Sarika began at Mountain Ash Comprehensive School, where she can wear the Kara, pending the outcome of her court challenge.
Her mother, Sinita, 38, has said that, although Mountain Ash is a good school, her daughter's education suffered as a result of the move and the stress involved in the run-up to her GCSEs. The family presented a petition to 10 Downing Street seeking support for the case and backed by 150 Gurdwaras - the main Sikh religious institutions - and over 200 Sikh organisations and 70 non-Sikh organisations. 100 MPs have also offered their support.
The hearing is expected to last three days.
Her parents knew the rules. Why do they think that the whole world should bow to their beliefs? Why not just stick to the rules, go to school, come home and wear whatever you want in your own time?
dave, london,
Why has this gone to court? The school doesn't discriminate on it treats all pupils equally no one is allowed religious items. If they try it on human rights grounds of denying an education, all the act says is the have to have an education not that it has to be at a specific school.
Stephen, St. Ives, England
The issue here is whether she is required to wear it by her religion.
A cross is not a requirement of Christianity but I understand that the bangle is. It's my guess that she will win her case in this instance. Really it is a scandal that proper guidelines haven't been issued by the government yet
andre , St Albans, UK
They had better not allow the bangle as a Christian woman was not allowed to wear her cross at work. All religious symbols need to stay out of schools if that is the schools rule. Otherwise one is holier than another or belongs to a different gang.She needs to obey the rules. She is a child.
Abigail, Torquay, UK
I am atheist, does that mean if i were at school i could simply invent some 'dress code' of my own religion? At what point does a religion become recognized to the extent you can flout generally accepted rules? As i believe all religion is akin to believing in fairy's I find this offensive!!!
Matthew, Bristol,
Here we go Human rights again. If this girl wants to wear her bangle at school, fine, then find a school that will accept it. How can she be allowed to waste so much money from legal aid for something that has absolutely nothing to do with the everyday British citizen.
This is all down to Blair.
John Moore, Paphos, Cyprus