They want a more equitable system of allocating cash, which will consider schools' pupil intakes, their location and other social factors. They also want a stable year-on-year formula that would enable heads and governors to plan ahead and prevent schools from accumulating huge reserves. It is estimated that #163;500 million has been squirrelled away by schools.
The call comes from Doug McAvoy, general secretary of the National Union of Teachers, and Ronnie Smith, leader of the Educational Institute of Scotland. It coincides with the publication of a report on education funding across Europe.
The study, carried out for the two unions by Coopers amp; Lybrand, found huge discrepancies between the amounts of money allocated to schools by governments and the actual needs of schools across Europe. The proportion of public expenditure and national income spent on education has declined in many countries.
Mr McAvoy said the findings had implications for Britain and warned ministers to act swiftly in case their commitment to "education, education, education" starts to appear meaningless.
He said that all new Government-inspired initiatives should be costed in the form of business plans and that adequate money be provided to schools for implementation.
In addition, the two unions are calling for annual targets to increase the amount spent on schools and a review of whether existing funding mechanisms are meeting needs.
The leaders believe that Britain should spearhead a debate on effective funding systems across Europe, which would be launched to coincide with the UK presidency of the European Union.
The NUT study, called "European Comparisons in Education Funding", found that Britain had the second highest proportion of public expenditure going into primary and secondary education, after Ireland. However, Mr McAvoy said this should not signal complacency on the part of ministers.
"No other government in Europe has set such stringent targets, or has such a detailed national curriculum or is as centralised in terms of initiatives. When you take the financial impact of all of this into account, together with the unpredictabi lity of the system from year to year, then the reality is that our schools are seriously underfunded," the NUT said.
He accused the Government of having only a "lukewarm interest" in reforming funding, although he acknowledged the additional cash made available for the next financial year from reserves.
Teachers in Scotland, meanwhile, are concerned that the extra money will be clawed back through local authority budgets cuts.
EIS general secretary, Ronnie Smith, said the Government had to "connect the words and aspirations with the deeds.
"If setting targets has become the favoured way of raising standards, then schools have to be given the wherewithal to deliver. We need more than a one-off act of generosity," he added.