Headteachers are to warn MPs that school budgets in England are facing “breaking point” after a combined £2.8bn in cuts and costs imposed upon them by the government.

The National Association of Head Teachers (NAHT) is writing to all Westminster MPs to highlight the plight of state schools in England suffering from funding shortages, in which it tells the politicians that standards are at risk.

The letter contains a blunt plea from Paul Whiteman, the NAHT’s general secretary, for MPs to lobby Philip Hammond, the chancellor, and ask for more resources for schools ahead of next month’s autumn statement.

“The autumn budget is the last chance for money to make it to schools this year,” Whiteman said. “Please write to the chancellor of the exchequer to ask him to announce more money for schools.”

Privately, school leaders are concerned that Brexit and other education issues – especially university tuition fees and student loans – are crowding school funding concerns off the political agenda.

With the Department for Education and the Treasury having already made major concessions on student loans, and with the possibility of more to come, headteachers fear there are few resources available for schools.

Whiteman said he believed the message had not been getting through to MPs about the extent of the crisis in schools, despite education being “a vote-changer for nearly a million people on polling day” at the last election.

In his letter, Whiteman tells MPs: “I’d be very surprised indeed if you hadn’t heard from a headteacher or a parent expressing concerns about school funding over the last few months.

“And yet, there’s a concern amongst school leaders, that despite the hundreds of letters written, and the thousands of parents, families and governors who have become campaigners, many MPs have failed to grasp the severity of the issue.”

The NAHT also plans to have members lobby parliament directly later this week. It has detailed how changes by the government since 2015 has resulted in £2.8bn being taken out of school’s frontline budgets.

The changes include national insurance and pension increases that have cut teaching budgets by 5.5%, as well as £600m-worth of cuts made to the education services grant used to fund services such as facilities management and legal advice.

Promises of higher pay for teachers will also have to be met out of current budgets, making the situation worse.

The letter to MPs also points out that many schools and academies will have to pay a further 0.5% cut of their payroll for the government’s new apprenticeship levy.

The DfE has already announced an extra £1.3bn for schools between 2018-20, but the headteachers argue that is still below the further £2bn a year schools need to keep their budgets at the same level as 2015-16.

The NAHT’s campaign follows last month’s move by 4,000 headteachers to write to parents, telling them there is “simply not enough money in the system” to fund schools properly.

In response, the DfE said the new national funding formula being introduced by the government, alongside the extra £1.3bn announced by the education secretary. Justine Greening, would see funding distributed more fairly to each school.