This was balanced by the 2,633 who entered teaching, but the vast majority of them - 1,603 - were newly qualified and in their first appointments.

These trends, which will be monitored more closely than ever by ministers because of their commitment to cut class sizes and recruit more teachers, were reinforced by the number of vacancies. There were 344 empty posts in secondary schools last September, a figure which has been steadily creeping up. This includes 92 vacancies that have been unfilled for more than three months.

The total number of secondary vacancies represents only 1.5 per cent of secondary teachers, but it includes 40 vacancies among maths teachers and 42 among English teachers. These are key specialists to attract into the profession, given the commitment to reduce sizes in S1-S2 English and maths classes to 20 by 2007.

The primary sector, too, needs to retain a healthy level of applications to meet targets of reduced class contact time for teachers and the new limit of 25 pupils in P1. Vacancies were running at 282 last year, including 89 which were not filled within three months; 81 were for headships or depute posts.

The other important factor in calculating teacher requirements is falling rolls. Pupil numbers are expected to decline over the next 10 years by 8 per cent among pre-school children, by 16 per cent in the primary sector and by 15 per cent in secondary.

This shrinkage will undoubtedly come to the aid of the Scottish Executive in meeting its commitment to have a teaching force of 53,000 by 2007.

Current numbers have risen from 50,534 in 2000 to 51,442. They will peak in 2007 and, if they keep pace with pupil projections, will fall to 48,998 by 2013.

Having put all these complex estimates into their calculator, the statisticians anticipate that an additional 1,400 pre-school and primary teachers will be required in 2005, increasing to 1,700 by 2007, falling back to 1,000 in 2008 and then rising thereafter to fill the gaps left as older teachers reach retirement.

Intake figures for the 2004-05 academic year, announced last week, will feed 1,000 newly qualified teachers into primary schools in 2005, compared with the 1,400 required, via the one-year primary postgraduate course which will have an extra 330 places. The BEd programme will take the 700 students entering this year four years to complete.

In the secondary sector, an additional 1,300 teachers will be required in 2005, 1,700 in 2006 and 1,500 in 2007. The numbers will fall off to 900 by 2008 and then rise to keep in step with the age profile of the profession.

The main postgraduate secondary intake has been increased by 355 places to 1,305, while secondary BEd courses will add another 202.

The planning group’s report predicts that its estimates of additional numbers will allow ministers’ pledge of class size reductions in primary and secondary schools to be met.