Can you find the teachers to sack?

For schools to have to make teachers redundant is evidence of a woeful failure of the political stewardship of education. But for many secondary heads, particularly in the South East, the problem is exactly the reverse. They can't get staff because they're not available. They're not coming forward when vacancies are advertised or they're leaving after a year or two.

This deep-seated fault in the educational landscape is far more damaging than the effect of civil servants and politicians making a hopeless mess of the figures. It is a chronic phenomenonleading to long-term instability in many schools. Unless it is addressed, the Government has no chance of meeting its aim of raising standards in weak schools.

The problem is at its most acute in the shortage areas, such as maths and science. "It's almost impossible to get maths and science teachers," says a secondary head in a Home Counties comprehensive. "And it's getting worse, not better." Like countless heads in the South East, he still has gaps in his maths and science departments for next September. This is at a time when nearly all qualified teachers in these subjects already know where they are going to be working in the autumn term. There are no more teachers out there. "There's moaning and groaning in all areas in maths," says Celia Hoyles, professor of mathematics education at the Institute of Education in London.

She is on the Advisory Committee on Mathematics Education, which was set up in 2002 and recently reported on "an acute shortage of maths teachers". Physics graduates working as teachers are an even rarer commodity. The list of shortage subjects continues to grow. It comprises most of the core subjects: maths, science, modern languages, design and technology, IT - and ENGLISH! We've reached a stage where we can't give our schools enough teachers of our own language!

Compare this to France, where if you want to be a teacher, you have to sit a competitive exam with hundreds of others and, each year, only the best get a job. Result? They don't have teacher shortages and the vast majority of their young people get a high quality education. Just as serious is the high rate of teacher turnover in so many schools, which has an insidiously damaging effect on children's education, particularly for those already short of stable influences in their lives. I know schools where it is not unusual for a quarter of the teaching staff to leave at the end of each year, and where it is the exception for pupils to be taught by the same teacher in consecutive years.

Pupils need to build on relationships with their teachers. If these are absent, the effect on learning and behaviour is marked. This, for me, is where successive governments have failed in the long-term development of adolescents.

It would be bad enough if confined to poor and crumbling inner city housing estates, but it is not. Take Surrey: an affluent county with stable schools and academic tranquillity? Not so. Surrey's turnover rate is the highest in the country.

The current drive to do something in London might have its good points but it will undoubtedly make things worse in the surrounding counties. I am not saying that nothing is being done. One area where there has been a clear improvement is in the numbers attracted to teacher training. Applicants for places on PGCE courses are up, due in part to the bursaries on offer. But it's no good recruiting and training teachers if they don't stay to do the job.

Three years ago I was one of 13 idealistic people starting a maths PGCE course at a London college. Only seven of us will still be teaching in or near London this September. Of the rest, three have dropped out, two have left the UK and one has gone to teach in Devon. Not all schools face these problems. I could also point to numerous schools where turnover is low, and where most vacancies attract enough candidates. Fine. But that doesn't alter the fact that thousands of children are getting a raw deal because of our inability to get staffing right.

The writer teaches maths in the Home Counties