The Liverpool case is the first to bear out what was feared might happen after last year's JFS court case: that a Jewish child eligible to get into a Jewish school under the old admission rules would end up being denied a place under the new system.
Previously, many schools would have accepted you simply if your mother was Jewish. But a year ago the Court of Appeal - in a decision upheld by the Supreme Court -ruled that the policy fell foul of the Race Relations Act.
Since Jews are legally defined as an ethnic group, the judges argued, parental descent is a matter of ethnic origin, not religious status, so it cannot be used to decide school admissions.
Schools, however, are permitted to give priority to pupils according to religious observance. So Jewish schools hastily had to revise their entry regulations and, as in most Christian schools, adopt faith-based tests.
At the time, the Board of Deputies warned that this could place non-practising Jewish parents "at a disadvantage". Most Jewish schools tried to minimise the risk by keeping their entry demands low, requiring evidence only of a handful of synagogue attendances in the few months before entry and a little previous Jewish education (at nursery, cheder or with a private tutor).
Despite headaches for synagogue administrators - who had to devise ways to register synagogue attendance - the new rules bedded down well and schools have not reported an adverse effect on their recruitment.
Some even began to see a silver lining. Simon Hochhauser, president of the United Synagogue, commented recently that many synagogues had benefited from seeing people show up who otherwise would not have come.
But Kayleigh Chapple's rejection by King David High School has now revealed the pitfalls - and in bizarre circumstances, since only nine of the 90 first-year pupils accepted in autumn will actually be Jewish.
King David will say that having been forced by the Appeal Court decision to draw up new rules, it is not in a position to bend them, even if the consequences seem perverse.
But Kayleigh's case will certainly add ammunition to those who believe the court ruling pernicious and want it overturned through a change in the law.