What is it about maths? A review of private tuition, presented by Judith Ireson at a recent research conference, has revealed that mathematics is the most frequently chosen subject, not only in England but worldwide. Why this widespread anxiety?
First, the way mathematics is organised in English schools exposes failure.
From the age of five, children will generally be seated in attainment groups for the subject, and more children are in sets for maths in upper primary and secondary schools than for any other subject. Evidence suggests that setting leads children to believe that they are inadequate and widens the range of attainment. Even in top sets, pupils worry about keeping up.
This labelling by group is reinforced by national test levels awarded not only in Years 2, 6 and 9, but also now on "optional" national maths tests in intermediate years. Target-setting alerts parents of six-year-olds to the levels that their children are likely to achieve at 11, 14 and GCSE, while booster classes identify pupils as at risk.
With this amount of information flowing through the system, parents of all but the highest fliers may be accused of irresponsibility if they do not take some action to lever their child into a higher trajectory, and a higher group or set.
But this doesn't explain why maths is also the most frequent subject for private tuition in countries that are less neurotic about setting and testing. In England, language is also subject to national testing and target-setting but generates less private tuition. This suggests that there is also something about how mathematics is universally taught and examined that convinces children that they are weak.
In many countries, including at GCSE in England, poor examination design ensures that success rates are lower in maths than language, giving pupils of the same relative attainment in both subjects the message that they are less successful in maths.
Whole-class oral questioning, common in many countries but now introduced here by the national numeracy and key stage 3 strategies, can mercilessly expose the less confident.
Teachers here and in many other countries are expected to rush through the curriculum at a precisely specified rate to cover the content in the tests, regardless of the children who haven't quite grasped one idea before they meet the next.
Even more able pupils experience feelings of failure as they speed to GCSE a year early or grab an extra GCSE in statistics on the way. And in every classroom or homework question, some answers are indisputably wrong, however kindly your teacher tries to disguise it.
Lack of achievement cannot be ignored by parents since mathematics steadily increases in importance for those wanting entry to selective state or private schools, access to skilled jobs, to higher education in a wide range of subjects and to top careers.
Although they may feel competent to help with English, in many cases parents' own sense of failure in school mathematics is likely to persuade them to take steps to avoid their child repeating their own experience, and to hire someone else to help.
In the Leverhulme Numeracy Research Programme we found one Year 6 class in which about half the pupils received private tuition, although most Year 6 children were working through books at home borrowed or bought from local bookshops in preparation for the Sats. These varying levels of external support mean that using national test results to evaluate schools is problematic.
Finally, does it matter? Not if it gives children extra competence and confidence, although it can instead build up anxiety and negative attitudes to the subject. It could also be damaging if we rely on parents to compensate for the negative effects of national arrangements for teaching and testing mathematics, rather than working to make these optimal for the learning of all children, even those whose parents cannot afford the fees.
Margaret Brown is professor of maths education at King's college, London