Last summer, as the politics of Britain’s exit from the EU staggered on and England’s World Cup run offered some kind of respite, I spent an afternoon in Brownhills, near the West Midlands town of Walsall. I was there to try to get beyond the deafening inanities of Brexit, and report on the mounting financial crisis facing England’s education system. At Millfield primary school, everything once again became clear.

Millfield serves a deprived catchment area, and is the kind of place whose everyday magic becomes obvious as soon as you walk in. It has an imaginative approach to education and a track record of helping children in difficult circumstances. Despite its location among tarmac and trunk roads, it specialises in outdoor activities such as canoeing and hiking. But the day I was there, all the talk was of which bits of its provision would have to go. Its headteacher, Michelle Sheehy, was blunt: “We’re heading for a £200,000 deficit. So we need to cut.”

When I spoke to her last week, Sheehy told me that some of the financial gap had been filled by her second job as the executive head of a school down the road, meaning she can spread her salary across two budgets. Music lessons have been hacked back. To keep vital extracurricular activities going, her staff have become used to giving their time for free. She now faces the prospect of losing the council-provided support for children with behavioural issues, and having to find and fund such help herself. Millfield is also crying out for renovations, not least to a “decrepit” set of toilets, which are being endlessly postponed.

In September last year she took the heartbreaking decision to cut all speech and language support, to save around £10,000 a year. “It’ll have a big effect on how some children perform in the future,” she said. “It’s a huge issue for us.” What might happen next, she went on, is something she tries not to think about. “I can’t even imagine four or five years’ time. I’m not looking ahead at all. And I don’t believe it can carry on like this. Something has to be done, otherwise the education system’s going to implode.”

Millfield’s story is one small part of a crisis in England’s schools – repeatedly highlighted by the Labour party, testified to by teachers, but still absent from the national conversation. The root cause is a huge lack of money. But around this financial black hole swirls just about every element of current education policy, as well as the attacks on the welfare state that have left schools and teachers trying to ensure that children are provided with not just pens and pencils, but the basics of subsistence. To say that the whole story proves once again that the Conservative party is never to be trusted with state education is true, but risks understating what has happened. This is a scandal, and it is time the politicians responsible were called to account.

Ignore the ministers who assure anyone who will listen that school spending has never been higher. Listen instead to the Institute for Fiscal Studies, whose figures prove that in England, total school funding per pupil between 2010 and 2018 fell by 8% in real terms. As Kevin Courtney, the joint general secretary of the National Education Union, emphasised in a speech last week, spending on education as a percentage of GDP (which encompasses both schools and universities) has come down from a peak of 5.8% in 2010 to barely more than 4%. This is much the same level as back in 1960 – when, as Courtney pointed out, “young people left school at 15, not 18 [and] tiny numbers went to university”.

Schoolchildren queuing for toast at Our Lady & St Werburgh’s Catholic Primary school in Newcastle-under-Lyme. Photograph: Alamy

Over the last decade or so, pupil numbers in England have risen by about 10%. At the same time, costs such as teachers’ pensions, national insurance contributions and the apprentices levy have been increasing at speed, and recent government pledges to help so far amount to cold comfort. The everyday consequences of the resulting cuts are plain to see, but in a very 21st-century way, the breathtaking stories somehow fail to cut through.

Every day seems to bring a new one. In a survey recently published by the educational charity, the Sutton Trust, two thirds of secondary heads said that financial pressures had forced them to cut teaching staff. As evidenced by reports that go back at least a year, about 25 schools in England have shortened the school week, so that pupils go home at lunchtime on Fridays. Early April brought news of a school in West Yorkshire that has introduced a once-a-week “dark day” when all the lights are turned off. I’m actually going to write that again. Early April brought news of a school in West Yorkshire that has introduced a once-a-week “dark day” when all the lights are turned off.

These cases blur out into a mess of other stories that involve schools across the country. There are those that have suffered huge cuts in funding for buildings and maintenance, thanks to a 41% real-terms cut in capital spending on schools since 2010. According to a recent story published in the education news outlet Schools Week, 46% of teachers in a survey of maintained schools said they “had buckets set up to catch drips”. In another poll published last week by the teaching union NASUWT, a fifth of teachers said they paid for vital resources such as paper or books at least once a week – and 45% said that during the past year, they had paid for some pupils’ “basic necessities”: food, toiletries, clothing.

Meanwhile, councils’ budgets for special educational needs are falling way short of actual demand – but under the additional pressures of inspections and test results, many schools and teachers have no option but to try and avert their eyes from an endless array of problems, grimly double down on what the curriculum demands, and do whatever they can to keep their schools afloat in all-important league tables.

This is one of the factors behind yet another aspect of the schools scandal: the fact that 49,000 children and young people who were at school between 2012 and 2017 are now understood to have been “off-rolled” – permanently or temporarily removed from a school, either to save money, or to keep average exam scores up. The pressure to meet targets in the most cash-strapped circumstances also partly explains why around one in five teachers reportedly expects to leave the profession in less than two years, and 40% of teachers, school leaders and support staff want to quit in the next five: further proof of morale crisis that goes back years.

And if you want a case study in the awfulness of modern education policy, look no further than Baron Agnew of Oulton, the 58-year-old alumnus of Rugby school and businessman who, as if to highlight the smooth workings of our 21st-century meritocracy, is a minister at the Department for Education. Last year, he said he was “like a pig out hunting for truffles when it comes to finding waste in schools”. The baron bet headteachers a bottle of champagne that advisers dispatched by the DfE could find proof of needless spending.

Three weeks ago came news of the kind of thing he had in mind: among 20 schools visited by his “school resource management advisers”, some had been variously told to replace teachers with support staff on limited contracts, teach some classes three at a time in a dining hall, keep half of any money they raised for local charities – including a children’s hospice – and, when it came to lunch, submit to “reviewing the portion size”.

These are plotlines worthy of Charles Dickens, enacted by people who mix the condescension of Victorian worthies with the flimsy vocabulary of management consultants. In eight years flat, they have inflicted damage on the school system – and, by extension, society and the economy – that may take decades to repair. Meanwhile, the future speeds on. And you wonder: if the Tories remain in charge, how will a country run by people so deluded and inept even begin to cope?

• John Harris is a Guardian columnist