Nigel Burgoyne, headteacher at Kesgrave High School, said only growing student numbers is keeping afloat his “painfully tight” budget for 2017/18.

Education secretary Justine Greening faces growing pressure to abandon or reform the national funding formula (NFF), set to be introduced in September 2018.

Suffolk’s school block funding would rise by £10m to £393m, remaining in the bottom 50 in England. The NFF calculates per-pupil funding, per school, based on factors such as low prior attainment and deprivation. It replaces the previous “postcode lottery” around the country.

But 56 of 300 schools would be NFF ‘losers’, suffering budget cuts of up to 3%, mainly primary schools in deprived areas of Ipswich and small rural schools, losing £1.2m between them.

Experts believe most other schools would suffer real-terms cuts anyway, due to inflation, rising pension contributions, and other ‘stealth taxes’.

Ministers say the NFF is not designed to help historically low-funded areas. But budgets are already under inflation pressure.

Mr Burgoyne said: “All schools are experiencing bigger classes and are struggling to keep on top of school maintenance.

“My greatest concern is that the quality of provision in all of our schools will start to suffer because we are having to heap more pressure on all of our staff.

“There is pressure to modify the NFF because the original proposals were not fair. We don’t expect to get paid the same as a same-sized school in Hackney which gets a million pounds more than us a year. But there still needs to be justice around the funding.

“There is ongoing dread because school reserves are pretty much used up. Where schools don’t have growth, they are on the verge all the time of financial difficulty. If they are hit by a big bill for something, that makes it a stressful existence. (The dread) is universal in Suffolk.”

Nationally, it has been reported that schools are scrapping music lessons, turning off heating, and planning to charge children for sessions with mental health counsellors.

Colin Walker, principal of St. Alban’s Catholic High School in Ipswich, said: “Suffolk schools are experiencing a desperate financial situation, of which we are no different.

“The government needs to recognise the enormity of the problem and undertake an urgent comprehensive review of school funding.”

Gordon Jones, cabinet member for education at Suffolk County Council, has previously written to all Suffolk MPs to gather support and vowed to continue fighting for fairer funding.

He said: “Whilst Suffolk will see an increase in funding under the proposed formula, this will not compensate schools for the years that they have not had an inflationary increase in their funding. In real terms, Suffolk’s schools will be lower funded than five years ago.

“We await the government’s announcement about the National Funding Formula, which is expected later this month, with interest.”

Ms Greening has previously told MPs that the Government recognised concerns during the General Election about the “overall level of funding in schools, as well as its distribution”. She hinted per-pupil funding could rise for secondaries.