Ministers will draw some long-term financial comfort from the estimates which have been reconfigured following the post-McCrone agreement and fresh input from local authorities on the realities of teacher supply. But the Executive still admits predictions about teacher supply and intakes to teacher training are far from an exact science.

Statisticians have balanced the employment of more teachers, particularly in primary over the next five years, against larger numbers of retirements and the sharp fall in pupils entering school. The equivalent of a whole year group - more than 50,000 children - will vanish from primaries, freeing teachers.

Last September, 425,000 pupils were in primary but by 2011 there are likely to be 13 per cent fewer at 368,000. Even in secondary, where a slight rise is predicted in the short-term, there will be 10 per cent fewer pupils within 10 years, down from 317,000 to 286,000.

Executive figures suggest the number of primary teachers will rise from 22,400 to a peak of 22,800 in 2006, the final year of the McCrone agreement. In between, numbers rise one year and dip the next but the Executive wants demand “smoothed” to allow teacher trainers to plan intakes “in an orderly fashion”.

Towards the end of the decade, the number of primary teachers will decline steadily to 22,000. The pattern is more constant in secondary where a current workforce of 24,600 will rise to 25,000 within three years before falling away gradually by 7 per cent to 22,900 within 10 years.

Planners say very low birth rates are likely to accelerate over the decade.

The estimates on teacher supply include two major elements from the McCrone deal: the phased reduction in class contact time to 22.5 hours and the cut in probation to one year. Newly qualified teachers will be in class for only 70 per cent of the time.