It's the old story of lies, damned lies and statistics - and statistics about teacher workforce planning are as bewildering as they come. Fiona Hyslop tells the education committee that half of all teachers will leave the profession over the next four years and that the Government will have to replace them. Crudely, this statement appears to be based on projections that around 6,000 teachers will leave every year - and if you multiply that figure by four, you come to just under 25,000, which is around half of the total teacher workforce of 53,000.
Ergo, there are bound to be plenty of jobs for the new teachers who have just come out of training - a case of jam tomorrow.
There is, however, a flaw in this argument. A glance at last year's statistical bulletin shows that, in 2007, there were only 10,144 teachers aged 55 and over. Even allowing for some of the 10,697 teachers in the next age-band (50-54) falling into the retirement bracket in the following few years, that would not take us anywhere near 25,000 retirements.
So how were the rest of the teachers leaving the profession, we wondered? Some went on maternity cover, we were told. But then we learned that, of the 6,000 teachers who leave each year, 2,000 do so after completing short-term contracts. That puts an entirely different complexion on matters - for they are not vacating jobs to which new entrants can aspire, nor are they necessarily leaving teaching permanently.
We are faced instead with 16,000 potential retirements and 20,000 teachers being trained over the next four years. Waiting in the wings are thousands of teachers who have left after short-term contracts dried up. For all the new, and newish, entrants to teaching, we can only hope that the promised class-size reductions are indeed implemented sooner rather than later - and that they convert into permanent jobs rather than short-term contracts.