Heads have cautiously welcomed the Conservative Party's plans to boost school spending by £4 billion by 2021-22, but warn that the move may simply amount to "shuffling money arround".
Geoff Barton, general secretary of the Association of School and College Leaders, said: "We welcome any improvement to school funding, but unfortunately the Conservative pledge of a £4 billion boost includes a large element of sleight of hand.
"The schools budget would have to increase by about £2.8 billion in any case because the pupil population will rise by 490,000 by 2022. So, the ‘extra’ money is in fact just over £1 billion, which is not enough to counteract the rising costs which are hitting schools and will amount to £3 billion a year by 2020.
"We calculate that the schools budget would need to increase by a total of between £6 billion and £7 billion to counter the impact of rising costs and implement the planned National Funding Formula in a way which is truly equitable."
"It's reassuring that they recognise the urgency of the funding issues. This was about people losing their jobs.
According to the Tories, the cash injection would amount to a £4 billion real-terms boost by 2021-22, made up of an extra £1 billion a year from 2018-19, on top of existing spending plans.
The money would come from scrapping universal infant free school meals (£650 million), introducing "better systems" for the student loans companies (£200 million), Whitehall "efficiencies" (£160 million) and the levy on sugary drinks (£10 million).
Mr Barton told Tes: "We won't be supportive of [the Tory plan for school spending] if what it's essentially doing is taking the overall education budget and simply shuffling money around."
The Conservatives say the extra money would mean no school would lose money under the new national funding formula, set to be introduced from next year.
The Institute for Fiscal Studies has estimated that this would require an extra £350 million per year. Protecting schools from real-terms funding cuts, however, would cost £1 billion in 2018-19, the IFS estimates.
'Taking money out of primary schools'
ASCL is supportive of the Tory party's plans to replace universal infant school meals with breakfast clubs, but Mr Barton is concerned that the extra money for schools is primarily coming from elsewhere in the schools budget, "taking money out of primary schools".
He also questioned whether the "efficiency savings" would be made, but said overall he was "cautiously optimistic" about today's announcement.
Jules White, headteacher of Tanbridge House School in West Sussex, said a planned governors' strike in his area would still go ahead tomorrow, despite the promises of extra cash for schools.
The strike will involve governors staging "sit-ins", issuing statements calling for more funding, and refusing to carry out voluntary duties, he said.
Mr White said that it remained to be seen whether the extra money would be enough to cover the real-terms cost increases affecting schools, such as those relating to national insurance, salary bills and the loss of the £600 million a year Education Services Grant.
He raised the question of how the extra money would be targeted. For example, if the money is mainly geared towards the schools that would have otherwise lost out under the formula, it could leave "under-funded" schools struggling.
Mr White's own school would gain 2.9 per cent under the proposed formula, but still has to find £260,000 in "unfunded costs", he said.
Schools across 15 counties are set to take coordinated action tomorrow, which will involve heads writing to parents about how they can quiz prospective MPs on school spending plans, on the doorstep.