There will be a shortage of 90 places a year at state-aided Jewish secondary schools in north-west London over the next few years, according to fresh estimates released this week.
The number, which represents the equivalent of three additional classes, would not be enough on its own to fill a new Jewish school.
But Partnerships for Jewish Schools, which commissioned the new research, acknowledges that there could be a further rise in demand.
Representatives of Jewish secondary schools were due to meet Pajes on Wednesday night to discuss how to react to the need for extra places if Jewish children are not to be left out in the cold.
A group of parents have already announced that they are planning to apply to open a new Jewish secondary free school in the area in 2018, while a second group have also been considering an application.
There will be a shortage of 90 places a year
Earlier research done for Pajes this year suggested that there could be as many as 135 more children applying to state-aided Jewish secondary schools in north-west London by 2022, owing largely to a rising number of children in local Jewish primary schools.
The estimates have now been refined by further analysis from the Institute for Jewish Policy Research, which looked more closely at first-preference applications to Jewish schools from parents.
Pajes believes that there will be a shortage of 90 places in the four mainstream state-aided Jewish high schools - Hasmonean, JCoSS, JFS and Yavneh College - in north-west London over the next five years. But the rise in primary school numbers could lead to a "further increase in demand".
While there is also growing demand within the Charedi population, this is unlikely to affect the mainstream Jewish school intake with the "partial exception" of Hasmonean, according to Pajes.
Overall, just under two in three Jewish children are applying to mainstream Jewish secondaries in London (including King Solomon in Redbridge, which now takes a minority of Jewish children, and the private Immanuel College).
The statistics are not conclusive enough to settle the debate over whether there should be a new Jewish school.
Some argue that it would not be possible to have a new school without admitting more non-Jewish children into the Jewish state system as well. While some parents see no problem with that, others would prefer an all-Jewish environment for their children.
Under current rules, a Jewish free school can reserve only 50 per cent of its places to Jewish children - although it may be able to take additional Jewish children on different grounds.
One of the proposed free school groups, Barkai College, intends to submit its application this autumn. The second group, Kedem High, has yet to say whether it is going ahead with its application.
Another plan mooted by some is to move King Solomon from Essex to north London. But the co-chairman of the school, Richard Burack, said this week that the idea "hasn't been discussed with us. We are passionate about providing Jewish schooling in Redbridge and Essex."
As for this September, Rabbi David Meyer, Pajes chief executive, said "a significant number of additional places were made available across the community's schools, which has helped to reduce the increased demand somewhat".
But Kelly Ifrah, a parent who has been lobbying for pupils without places, said that she had passed to Pajes a list of 22 children still without a Jewish school. Her son, Yohann, finally received an offer from JFS last month.
Other children without a place were having to watch their friends getting uniforms and making other preparations for Jewish secondary school, she said.
"We as a community are isolating those children through no fault of their own because they didn't make the lottery and that's not right," she said. "My personal preference would be for JCoSS to open an extra class and take these children."