Nine of the leading judges in England and Wales this week grappled with the fraught question of who is a Jew as the legal dispute over entry to JFS finally reached the highest secular court, the new Supreme Court.

A three-day hearing before a packed courtroom opened on Tuesday with far-reaching implications not only for other Jewish schools but potentially for those of some other faiths as well.

Europe’s largest Jewish school is appealing against a Court of Appeal ruling made this summer that to offer places on the basis of whether a child’s parent is Jewish amounts to racial discrimination.

But Lord Pannick, leading counsel for JFS, told the judges — three of whom are believed to be ethnically Jewish — that the school’s decision was a matter of religion, not race.

The legal action began after JFS originally refused a place to a boy known only as M because his mother’s Progressive non-Orthodox conversion was not recognised by the Office of the Chief Rabbi.

Such is the importance of the case that at one point there were 14 wigged counsel

“M failed to secure a place at the school because and only because of the religious criteria applied by the Chief Rabbi as to who is a Jew,” Lord Pannick said. “These religious criteria do not depend on a person’s ethnicity.”

According to the law, faith schools can give preference to pupils on religious, but not racial, grounds. The Court of Appeal ruled that using parental descent to decide entry was unlawful because Jews constitute an ethnic group under the Race Relations Act.

But Lord Pannick contended: “There is a vital distinction between whether someone is Jewish according to Orthodox religious principles and the different question of whether someone is Jewish in the sense of their ethnic origins under the Race Relations Act.”

For the first time since the start of the legal action in mid-2008, the words of M — who has since been admitted to JFS — were heard in court in a written statement. An active attender at the London Masorti synagogue to which he and his father belong, he said that Judaism had been “part of who I am” since as long as he could remember.

At his previous, non-Jewish school, he said, “I had always been a bit of an odd one out because of my Jewish beliefs and values.” On the one occasion he had worn a kippah there, he had been “taunted”.

His mother — now divorced from his father — had been an Italian Catholic who converted to Judaism through a Progressive synagogue here before their marriage. But since non-Orthodox conversions are not accepted by the Chief Rabbi, M is not Jewish according to Orthodox definition.

A written statement was also handed in to the court by David Lightman, whose daughter Maya was rejected five years ago by JFS because her mother’s Israeli Orthodox conversion was also considered invalid by the Office of the Chief Rabbi. Her mother Kate is head of English at JFS.

“Maya remains very keen to attend JFS in the sixth form next year, if she is permitted to do so,” he stated. “For five long, hard and painful years, we have tried to fight for the right to send our child to the school of our (and her) choice.”

Such is the importance of the case that at one point there were 14 wigged counsel in court.

Apart from M’s father and JFS, five other organisations were allowed to intervene — a record for an appeal — with both the Board of Deputies and the Department for Children, Schools and Families querying the Court of Appeal ruling in submissions to the court.

At one point, Lord Phillips, Supreme Court president, asked whether someone sent to the gas chambers because their mother’s mother was Jewish was being persecuted on racial, or religious, grounds.

Later, the judges had to get their heads around the idea that someone might go to synagogue weekly, celebrate festivals and eat kosher — but might still not be religiously Jewish according to the Chief Rabbi.