Every state school in England will see budget cuts before 2020, even after new funding plans are put into place, research suggests.
The Education Policy Institute analysis looks at the impact of the new national funding formula against the backdrop of financial pressures in schools.
It finds even schools benefiting from the funding shake-up will see their gains wiped out by budget pressures.
The government insists schools funding is at a record £40bn level.
But the EPI estimates that average losses will reach £74,000 for primary schools and £291,000 for secondary schools by 2019-20.
This is because schools are bearing the brunt of unfunded rises in pay, pension and National Insurance contributions, which will account for between 6% and 11% of their budgets by 2019-20.
EPI chairman David Laws said a new funding formula was long overdue.
But he added: “As our analysis shows, however, the government may receive little credit from schools for these reforms – as even the schools benefiting from the new formula have their gains completely wiped out by other funding pressures.”
The report says: “There are unlikely to be any schools in England which will avoid a real terms cut in per pupil funding by 2019-20, even in areas benefiting from the new formula.”
The Conservatives promised, in their 2015 manifesto, a real-terms increase in the schools budget during this Parliament.
The manifesto also said: “Under a future Conservative government, the amount of money following your child into school will be protected.
“As the number of pupils increases, so will the amount of money in our schools.”
However, there is no requirement for the funding formula to be debated in Parliament – the secretary of state has the power to push through the funding formula.
Despite widespread concern over funding pressures, there was no extra money earmarked for school revenue budgets in the Budget last week.
Two days later, Education Secretary Justine Greening was heckled by head teachers at a conference in Birmingham.
The Department for Education maintains the EPI report underlines that the government was right to introduce school funding reforms and said it was consulting on the factors that will make up the formula.
According to a DfE spokeswoman, funding is set to rise over the next two years to £42bn as pupil numbers increase.
She added: “Schools will be funded according to their pupils’ needs, rather than by their postcode, with more than half set to receive a cash boost.
“Of course we recognise that schools are facing cost pressures, which is why we will continue to provide support to help them use their funding in cost effective ways.”
She said a recent report from the National Audit Office recognised that schools should be able to make savings without affecting educational outcomes.
In its assessment of the new formula itself, which was brought in to address historical inequalities between areas in schools funding, the EPI said the plans were unlikely to satisfy many lower funded areas.
The EPI also finds that pupils who live in the least deprived areas will experience the highest relative gains.
The parent-led Fair Funding for All Schools campaign urged the government to stick to its election promise to protect school funding.
“As parents, we see the damage being done to our schools and our children’s futures,” said the group in a statement.
“There is now enormous political pressure on the government to alter course.
“But tinkering with the National Funding Formula while leaving the overall budget unchanged will help no-one.
“You can’t achieve fairness by slicing up a shrinking pot of money.
“Furthermore, we will not accept a situation where the government merely readjusts the formula to appease its own backbenchers at the expense of others.”
‘Go back to the chancellor’
Malcolm Trobe, interim general secretary of the Association of School and College Leaders, said the government deserved credit for committing to a new funding formula because the current system was unfair and needed to be reformed.
“But the overall pot of money is too small and is not sufficient to meet rising costs,” he said.
Shadow Education Secretary Angela Rayner said head teachers were being forced to choose between cutting subjects or cutting the school week.
She added: “Less than two years ago, the Tories promised millions of parents that they would protect the money that is spent per pupil on their children’s education. This report shows that it is yet another manifesto promise they are breaking.”
Liberal Democrat education spokesman John Pugh said these proposals made schools scramble for the same pot of money.
“Schools in my own area have already written to me warning that they will have to cut staff numbers in order to avoid untenable budget deficits.”