There are nearly as many qualified teachers not in service as working in schools. But this headline figure - jumped on by the Conservatives a few weeks ago - is misleading in many ways. For instance, of the total, only 255,000 have ever worked in the maintained sector as a teacher, and of these, 130,000, or more than half, are in their 50s and have probably decided either to retire or to decelerate their career into supply or part-time work. By contrast, there are only 12,000 trained and experienced teachers who are under 30 and not in service in schools.

Many of the nearly 9,500 women in this career group may be taking a break for family reasons while others may be working overseas or in professions allied to education. Some will undoubtedly be working as teaching assistants either through choice or necessity.

The older teachers not in service will include everyone from teacher trainers to education officers, Ofsted inspectors - and even some politicians.

In addition to these teachers who have seen service, there are about another 89,000 who have not. Of these, 33,000 are in their 50s, and only 12,000 are in their 30s compared with 22,000 in their 30s and 19,000 in their 40s.

The small number in their 20s is a tribute to better recruitment to teacher training over the past decade, where only those who really want to teach have been encouraged to enter the profession. The days when the PGCE was regarded an insurance against a tough job market may have been a myth. At least until this recession hit the graduate job market.

John Howson is a director of Education Data Surveys, part of TSL Education.