Whatever the pros and cons of school league tables, they have probably done wonders for Jewish day schools. The proven academic track record of Jewish schools year in, year out, must be one reason why parents have been turning to them in ever-increasing numbers to the point that six out of every 10 Jewish children in the UK currently attend one.

Over the past two decades, thousands of new Jewish school places have been created, aided in no small part by the generous subsidies of successive Conservative and Labour governments for religious schooling. A change of government is unlikely to check the drive to open even more Jewish schools - although the Liberal Democrats are committed to "more inclusive" admissions policies for faith schools, which would mean having to accept more pupils from outside the school's designated faith.

Judged by their secular educational performance and their popularity with parents, Jewish schools are an undoubted success story. But ask what long-term impact they have on the Jewish lifestyle of their pupils and the answer is less certain because we simply do not have the evidence.

Twenty-five years ago, research carried out by Professor Stephen Miller suggested that Jewish secondary schools in some respects actually had a negative influence. Children at Jewish secondary schools were ritually more observant than Jewish pupils at non-Jewish schools, but showed weaker religious belief and appreciation of Jewish ethics. Their identification with Jewish peoplehood was no greater. (His research took into account the home environment).

Since then, Jewish studies may have improved with better teaching training and educational resources, as well as the creation of a Jewish inspection service. But remarkably, Miller's survey, as far as I am aware, has never been repeated, or if it has, the findings have not been widely circulated.

In a recent essay, Professor Zvi Gitelman noted that millions of dollars had been invested by philanthropists in Jewish schools in the former Soviet Union after the fall of Communism. But there had been no follow-up to see if the money had been well spent. "Why is the most enquiring people on earth so shy about making such enquiries?" he wrote (in Jewish Day Schools, Jewish Communities, edited by Alex Pomson and Howard Deitcher). "Perhaps donors and sponsors assume Jewish schools have to be a good thing so they don't need to see empirical outcomes. Or maybe they are too afraid to know the outcomes." It is a comment that could easily apply here.

For Jewish schools, the key test is not so much the amount of knowledge children come out with as how actively they are involved in Jewish life later as adults. In theory, it should be possible to take a cohort of graduates of Jewish schools and non-Jewish schools and compare what happens to them over time. Then we might know whether the claims that Jewish schools represent the best bet for Jewish continuity turn out to be justified.

Research, too, could help Jewish schools become more effective. It is reasonable to assume that Jewish education is more likely to succeed if what is taught in school is supported in the home. While there has been some investigation into why parents choose a Jewish school, it may help to know more about their attitude towards the Jewish curriculum. Do they rate Hebrew and history above Bible and halachah, for example, or are they indifferent to Jewish studies as merely the price their children must pay for attending a school with a good secular education?

Eli Kohn, of Bar Ilan University, writing in the same volume as Gitelman, reported on research done in a community high school in Canada, which found that students fell broadly into three camps. For one group, learning about Jewish practice and traditions was important: for the second, becoming proficient in Hebrew; while the third was primarily interested in contemporary issues such as Israel or Jewish communities around the world. So perhaps our own mainstream secondaries, given the diversity of their intake, might offer a broader Jewish programme, allowing students more scope to specialise in areas that interest them.

At least now there are signs that research is being taken more seriously in this country. Next Thursday, the UJIA is holding a day conference on the subject. It might not be so long, after all, before we are better able to answer the question: do Jewish schools work?