The annual survey, by the National Foundation for Educational Research, also found that teachers' workload was a concern for nearly all heads.

This was less so than in the past, but the government's new plan to extend the curriculum was seen as raising problems of staffing, money and time.

Given an imaginary 5% cash boost, most would spend it on classroom assistants.

Stability

The budgetary concern has been top of the list of concerns for the 11 years the survey has been conducted.

It worried 76% of the heads during this past year - down from more than 80% in 2003.

They welcomed the planned move to a three-year budget cycle, which they felt would lead to long-term improvements and greater stability.

The foundation sent questionnaires to 800 head teachers, 413 of whom responded.

After-school clubs

They were asked to indicate, from a list, additional services provided on their school premises.

More than three-quarters of schools (79%) had after-school clubs for pupils. Almost half allowed school facilities to be used by the wider community and about a third offered family learning and breakfast clubs - all activities of the sort the government is keen to expand.

The general secretary of the National Association of Head Teachers, David Hart, said: "Heads are absolutely right to be cautious about the amount of money in the system to deliver the government's flagship programmes.

"If they are going to fund childcare and extended provision there has to be additional streams of money on top of the cash which has been promised."

A spokeswoman for the Department for Education and Skills said: "We are backing significant school reform with significant financial investment. School budgets are at unprecedented levels."

Support

This year's survey was co-sponsored by the Local Government Association.

The chair of its children and young people board, Alison King, welcomed the fact that most head teachers felt that local education authority support for school improvement was either good or excellent.

However, more than a third of head teachers rated their LEA as not very good or poor at sharing practice.

Cllr King said: "Councils are delighted to receive such positive feedback from teachers because it means they are helping schools get on with the core business of teaching, leaving councils to worry about administration, improvement and training."