King Solomon High School in Essex is facing an increase in non-Jewish students this autumn in line with the predicted impact of more Jewish school places available elsewhere.
As many as 40 per cent of first year entrants to the state-aided comprehensive could be non-Jewish, according to rumours circulating at a Jewish education conference last week.
Spencer Lewis, King Solomon's head teacher, declined to release figures this week, but suggested that the composition of the intake would be exceptional this year.
He explained that this was because this year, one of the two Jewish local primaries which act as a feeder for King Solomon has a particularly small number of children in the last year.
"This means that for entry in September 2010, our admission numbers of Jewish students are fewer than we normally have and therefore we will be welcoming a cohort of non-Jewish students into year seven in September," he said.
"But as yet, we are not sure of the numbers."
But he added: "Looking at the numbers in our two main feeder Jewish primary schools in other, younger years, we can expect a much more robust number of Jewish students entering the school from September 2011."
The Jewish Leadership Council has forecast that there could be more places than applicants in mainstream Jewish secondary schools in London, with the opening of the new Jewish Community Secondary School in Barnet this September.
In the past, the school has benefited from an overflow of students from north-west London who were unable to win places at oversubscribed Jewish schools closer to home.
But the cross-communal JCoSS can now offer a further 180 places in north London.
Last September, King Solomon - which can take a maximum of 150 pupils in its first year - accepted seven non-Jewish students out of a total intake of 122 entrants.
A Jewish Leadership Council survey of Jewish parents in Essex suggested that the vast majority had no objection to non-Jewish children being accepted into local Jewish schools, provided their numbers did not amount to more than a quarter of the intake.
Mr Lewis commented that in view of the school's "resoundingly good" Ofsted report at the end of last year and "very good" examination results, "it isn't a surprise that we have a lot of interest from non-Jewish parents".
He said the school was "currently considering how we best include the year seven non-Jewish students in our Jewish studies curriculum." But he emphasised that "certainly nothing will jeopardise the Jewish and Zionist ethos, curriculum, and nature of King Solomon High School."