A court hearing has begun over a Jewish school's admissions policy, which may have implications for at least another 20 schools and other organisations.
JFS has said admission is a religious, not a racial matter
The JFS in north-west London is accused of discriminating against an 11-year-old boy it refused to admit.
He was rejected in favour of "committed atheists" because his mother was not regarded as Jewish, his family's lawyer told the High Court in London.
Seeking judicial review, Dinah Rose QC said the policy involved ethnic origin.
The state-maintained school is heavily oversubscribed. It gives preference to applicants whose "Jewish status" is confirmed by the United Synagogue.
The boy - named in court only as M - has a Jewish father. His mother converted to the Jewish faith before he was born but had been a Roman Catholic.
In the eyes of the United Synagogue the 11-year-old was not Jewish because his mother was not accepted as Jewish, Ms Rose told Mr Justice Munby.
She said JFS's current admissions policy was incompatible with the school's own religious ethos and admissions code.
Ms Rose accused the school of applying a test "not based on faith but wholly or partly on ethnic origins".
She said the issues raised by the case went to the heart of the national debate started by the Archbishop of Canterbury over the extent to which Islamic Sharia law should be accommodated by UK law, which prohibited racial discrimination.
Ben Jaffey, appearing for the United Synagogue, was allowed to address the court after saying that, if M and his father were to win their case, it would have "very serious potential consequences" for the synagogue.
He said it would affect not only the JFS but more than 20 other schools and other Jewish community organisations.
The British Humanist Association is supporting the family.
The hearing continues.