Almost one in six teachers is a leader. Of the 363,000 full-time regular teachers employed in schools, over 59,000 are paid on the leadership scale as either a head, deputy or assistant headteacher. During the past nine years, the number of school leaders has increased by about 7,000. This has mostly come about as the result of the creation of the assistant head grade. There were 7,000 assistant heads in 2001 compared with some 19,000 today.

The majority of assistant heads are still to be found in the secondary sector, where they account for about 60 per cent of school leaders. The rate of growth in the creation of new assistant headships has been slowing, with only 500 new posts created in 2008 compared with 1,100 in 2007.

There are also significant geographical differences in the availability of assistant head posts, with the grade being far more common in London and the surrounding counties than in the North of England.

While the assistant head grade has been growing, the post of deputy head has been in long-term decline from 21,600 in 2001 to 18,500 in January 2009, a loss of 3,100 posts in nine years. The bulk of the decline has been in the primary sector where there were 2,600 fewer deputy heads in 2009 than in 2001. This decline partly explains why some primary schools have difficulties in recruiting a new headteacher since heads are primarily appointed from among the ranks of deputy heads. Part of the decline has been due to school closures and amalgamations, as the total number of heads in the primary sector has fallen by 1,600 since 2001.

Despite needing fewer heads, finding them is still a problem for too many schools.

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