Although the Department for Education and Employment’s annual January survey has been criticised for under-estimating the staffing shortages, the official data-gathering system is at least consistent. Thus, it is possible to detect trends in vacancies, if not actual numbers, with some accuracy.

Vacancies as a proportion of the teaching force reached an all-time high in 1990, at 2.1 per cent of primary teachers and 1.5 per cent of secondary staff. But because recruitment improved during the years of recession, and funding for schools tightened, the vacancy rate was low between 199496.

The closure of the early-retirement route in the late 1990s resulted in a smaller outflow from the profession that balanced the effects of declining ecruitment. However, vacancy rates have climbed in the past year - in both the primary and secondary sectors. According to the DFEE survey, vacancy rates doubled in secondary schools during 2000 and rose by a third in the primary sector. Secondary vacancies now match the record levels of 1990, and in some subjects are higher.

This January, the DFEE recorded 410 maths teacher vacancies in England. This compares with just 279 for England and Wales in 1990. Happily, there were fewer languages teacher vacancies - 250 compared with 366 in 1990.

The prognosis for the future is poor, at least in secondary schools. The extra student-teachers recruited last year will be barely enough to keep up with demand, and the position is likely to worsen next year.

John Howson The writer is managing director of Education Data Services Int.edulineone.net.