Critics say the city’s schools are facing a cash crisis but council bosses have said there are plans in place to help manage their budgets.
Five schools had a deficit at the end of 2018/19 – including two secondary schools half a million pounds in the red – but that number is forecast to rise to 36 by 2021/22, council documents showed.
A further four schools are facing debts between £100,000 and £200,000.
Councillor Mike Hardacre, the city’s education boss, sought to play down fears over the dire forecasts and said it was not yet known how much cash would come from the Government for schools in the coming years.
He said the large deficits at the two secondary schools had been caused by “legacy issues” associated with the David Cameron government decision to scrap the Building Schools for the Future Programme. The schools were not named in the report.
Councillor Hardacre said: “At this moment that’s sustainable and there are robust plans in place to ensure payback for the few schools that are in deficit.”
He added: “This is part of a nationally arranged scheme. Money schools don’t spend stays with us to make sure schools which are in difficulty, we can deal with the problem over a period of time.”
Bob Stephenson, a former headteacher who is now a director at the Amethyst Academy Trust, which runs Aldersley and Moreton high schools, said the latest government funding did not make up for previous cuts.
He said: “Clearly there is a funding gap because the funding announced doesn’t cover the welcome pay rise, national insurance and pensions going up. Take all these things together frankly schools are going to be worse off in two years’ time.”
Chris Keates, acting general secretary of teaching union NASUWT, said: "Schools are seeing cuts in real terms spending per pupil for the first time since the mid-1990s which is having a detrimental effect on teachers’ employment and on the education of children and young people.
“However, the problem is not just underinvestment as NASUWT research shows that 90 per cent of maintained schools and 92 per cent of academy trusts have budget surpluses, which are now running at close to £4 billion across the system.
“The Government not only needs to invest billions of pounds more than it has promised to schools in order to reverse the cuts in per pupil funding, it must also bring to an end a system which allows some schools and academy trusts to continue to stockpile funding whilst others experience acute financial difficulties."
Julia Donald, from the Wolverhampton Lib Dems, said: “The idea that a school can be half a million in debt for just doing its job is a national scandal.
"I worry what the impact of this will be; shorter hours for schools, asking parents to raise cash or even ask parents to pay for basic things like books and stationery for their pupils.
“It is time the Government funded schools properly in the city.”