On a Thursday in January 300,000 secondary pupils were taught in a class of more than 30 for at least one lesson.
In spite of much hype about falling class sizes, not all teachers are seeing the benefits. The number of secondary lessons involving more than 30 pupils has almost doubled during the past 10 years.
In January, 30,000 more secondary pupils in England were being taught in classes of more than 30 than was the case in 1998.
Classes of 31 aren't any more unteachable than those with 29 pupils in them. However, the figure has come to be seen as a benchmark in England, above which classes are regarded as unacceptably large by teachers.
Average class sizes also fail to reflect the fact that smaller groups exist for special needs pupils, and for practical subjects, where safety in workshops and labs necessitates it.
This must mean that in some classroom-based subjects, class sizes may well be above the overall average. These subjects probably account for the 10,000 lessons with more than 31 pupils counted in the 1999 survey.
So far there is no breakdown by local authority of secondary average class sizes. And the chief inspector seems to have ignored this trend towards larger classes in his annual report.
Nothing seems to be known about who is teaching these larger classes. Do some teachers spend a disproportionate part of their week working with large classes? Do schools take extra marking into account when allocating preparation time?
Together with continued rising rolls, and the Government's priority in reducing key stage 1 class sizes, it is difficult to see the figures for January 2000 being any better than this year - and they might even be worse.
John Howson is a fellow of Oxford Brookes University and runs an educational research company. E-mail: firstname.lastname@example.org