The figures for the 2019-20 academic year have not yet been recorded, but if they are true to form, it is reasonable to assume that more British Jewish children than ever before will register at a British Jewish school next week.

The numbers have been rising steadily for decades, from just over 5,000 in the 1950s to in excess of 35,000 today.

That sevenfold increase is striking enough on its own terms, but when you bear in mind that the UK’s Jewish population has declined by about 30 per cent in size over the same period, it is all the more remarkable. Close to 70 per cent of all Jewish school-age children in this country are now in Jewish schools; only about 30 per cent are not.

Some regard this as a complete triumph. Confronted by the powerful forces of assimilation, weakening Jewish identity, declining levels of attachment to Israel and a growing sense of doom about antisemitism, most of us are choosing to immerse our children in the safe and comfortable educational environments of Jewish schools.

I am part of this; all of my children either are being, or have been, educated in Jewish schools.

And yet I have my doubts. It’s not entirely clear to me whether Jewish schools are actually having the desired effect.

When we have looked at it empirically, we can see that Jewish schools help to enhance young people’s Jewish social circles over time — and that’s not something to dismiss lightly — but their impact on former pupils’ levels of Jewish community participation and engagement are rather less clear.

Far more impactful are a strong Jewish home environment and long-term programmes in Israel — both of these have much clearer and more positive measurable outcomes.

But there is also a bigger picture to take into consideration. Geographically, we are becoming more concentrated. Many regional communities are in decline, due both to ageing and out-migration, as indeed are communities in certain parts of London.

By contrast, Jews living in north-west London and south Hertfordshire, not to mention Stamford Hill, Broughton Park and Gateshead, are living in more densely populated Jewish areas. We are thinning out across the country, and thickening out in a few small parts of it, all of which almost certainly means we have less face-to-face contact with non-Jews, and they have less face-to-face contact with us.

Jewish university students in the UK replicate this pattern with the choices they make about where to study — 50 per cent of them are based in just eight universities.

Religiously, we are closing in too. Well over half of those children in Jewish schools are Charedi. Close to half of all Jewish children born in the UK today are born into Charedi families. Slowly but surely, the balance between the the Charedi and non-Charedi Jewish populations is shifting.

The latter remain the clear majority at the moment, but assuming constant trends, that will change long before the end of this century. And Charedi Judaism, for all its many strengths, is fundamentally more insular, more inward-looking than other more open approaches.

The historian in me takes the long-term view about this, recognising that Judaism has continually taken inward and outward turns over time. Sometimes we have had to close ranks to concentrate on our internal needs and protect us from external threats; other times, we have opened ourselves up, proactively reaching out to wider society, absorbing ideas from outside and making them our own.

The story we most commonly tell ourselves is the one in which the outside world is hostile — what Salo Baron called “the lachrymose conception of Jewish history” — but in truth, there have been many periods when we interacted positively with wider society and indeed incorporated traditions from outside that we now commonly assume to be Jewish ‘mi-Sinai.’

Lighting yahrtzeit candles and covering our heads are just two such examples, the former originally being a Catholic German custom, the latter most likely an oriental one. The wider world is not exclusively threatening to us; it has enriched Jewish life too.

So as the new school year begins and a new Jewish year beckons, we find ourselves in rather odd territory. We still have more freedom to be ourselves than at more or less any previous period in history, yet our fears of the outside world — of antisemitism and assimilation — are driving many of us to batten down the hatches more and more. It feels safer and more comfortable to huddle together. But is it wise?

Jonathan Boyd is executive director of the Institute for Jewish Policy Research (JPR)