French Sikhs have accused the authorities of failing to honour an agreement exempting Sikh schoolchildren from a ban on overtly religious attire.
Sikh students leave a school near Paris after being turned away
At least five Sikhs wearing turbans or cloth covers for their uncut hair were barred from classrooms near Paris.
Teachers in the Seine-Saint-Denis region, north of the capital, say it is unfair to apply the ban to Islamic headscarves but not to Sikh headgear.
The French ban on symbols of faith in school came into effect last week.
The law - aimed at preserving France's secular ethos - caused outrage amongst Muslims who felt they were being unfairly targeted.
Christian crucifixes, Jewish skullcaps and Sikh turbans are also banned from schools, according to the law.
In talks with the French government before the schools reopened, Sikh leaders say they argued the ban should not apply to their turbans, which, they said, were cultural rather than religious symbols.
They said a compromise was struck whereby Sikh students would be allowed to wear a sort of under-turban - a simple cloth covering for the hair - instead of a full turban.
Ban proposed in December 2003 and backed by parliament in March
Came into effect at start of new school year on 2 September
Lays down that "conspicuous" religious items may not be worn in schools
Forbidden items will include Muslim headscarf, Sikh turbans, Jewish skullcap and large Christian crucifixes
Parents of the Sikh boys barred from attending classes are angry the agreement has not been honoured.
"My son was supposed to go to classes today," Gurdial Singh told French news agency AFP.
He said his son was able to enter the school but was "not allowed into the classroom".
"And yet he was wearing an under-turban, just a thin cloth for hiding the hair, just as we agreed with the authorities."
A Sikh community spokesman said talks were underway to resolve the issue with school authorities.
Most of France's Sikh community - numbering between 5,000 and 7,000 - lives in or around Paris.
Earlier this year, French Sikhs joined Muslim women in street protests against the ban on state-school students wearing conspicuous religious attire.