LONDON  The questions before the judges in Courtroom No. 1 of Britain’s Supreme Court were as ancient and as complex as Judaism itself.

Who is a Jew? And who gets to decide?

On the surface, the court was considering a straightforward challenge to the admissions policy of a Jewish high school in London. But the case, in which arguments concluded Oct. 30, has potential repercussions for thousands of other parochial schools across Britain. And in addressing issues at the heart of Jewish identity, it has exposed bitter divisions in Britain’s community of 300,000 or so Jews, pitting members of various Jewish denominations against one another.

“This is potentially the biggest case in the British Jewish community’s modern history,” said Stephen Pollard, editor of the Jewish Chronicle newspaper here. “It speaks directly to the right of the state to intervene in how a religion operates.”

The case began when a 12-year-old boy, an observant Jew whose father is Jewish and whose mother is a Jewish convert, applied to the school, JFS. Founded in 1732 as the Jews’ Free School, it is a centerpiece of North London’s Jewish community. It has around 1,900 students, but it gets far more applicants than it accepts.