Thousands of children will return to lessons tomorrow to find their school still has no permanent head teacher.
Figures published to coincide with the start of the new term show that the shortage of heads is at crisis point, with up to 700 schools unable to find well-qualified candidates. The situation is a blow to ministers who have repeatedly said that the key to raising standards is a good head teacher.
Government advisers have warned that, in future, schools may have to share head teachers because they are in such short supply. Head teachers say that fewer applicants are putting themselves forward than in previous years because of fears about the workload.
At least one in five of those schools who advertised for a new head last year failed to make an appointment, says the new research.
The recruitment crisis was worst in primary schools, where 28 per cent of all advertisements were unsuccessful. The figure for secondary schools was 20 per cent and 22 per cent in special schools.
The man who compiled the statistics, Professor John Howson, from Oxford Brookes University, said that the most needy pupils will suffer the worst, as it is often the toughest schools that struggle to find suitable head teachers.
"A lack of strong leadership can lead to drift, and a troubled school will lose support. I am in no doubt we have a serious crisis of leadership on our hands," he said.
The research was sponsored by the two national head teachers' groups. John Dunford, the general secretary of the Secondary Heads Association, said that government reforms were to blame for increasing the workload.
"People who might apply for headships see the hugely increased range of responsibilities and prefer to remain as deputies or middle managers," Dr Dunford said.
Experts warn that the situation will get worse as many teachers recruited in the boom years of the late Sixties will be retiringby the end of the decade.