Seventy-six per cent of secondary schools in Devon were judged good or outstanding, a drop of six per cent.

The report said: “By the end of August 2018, 83 per cent of schools in the South West were judged good or outstanding at their most recent inspection, compared with 86 per cent nationally.

“This was a four percentage points decline for the region compared with August 2017.

Parents are coughing up an average of £11 a month to their children’s schools to help meet education funding shortfalls, a survey has shown, and many are being asked to provide items as basic as stationery and loo roll.

The parents and education charity Parentkind commissioned a survey of 1,500 parents and found that two in five are asked to contribute to a general school fund, to be used in whatever way the school needs.

The average monthly voluntary donation by parents has increased by more than a quarter in a year, rising from a reported £8.90 in 2017 to £11.35 in 2018.

Of those who remained at UTCs, many made poor progress, with even previously high-achieving students performing less well in their exams, according to the Education Policy Institute.

About 60 UTCs have opened since 2011, after being championed by the Conservative Lord Baker and the then prime minister, David Cameron, enrolling students aged 14 to 18 and designed to encourage the study of science, technology and engineering.

But despite official encouragement and lavish funding, they have failed to generate enthusiasm among parents, and 10 have subsequently closed or converted into conventional schools.

David Laws, the EPI’s executive chairman, said after spending “hundreds of millions of pounds” on UTCs, the Department for Education (DfE) should halt any further expansion until their effectiveness has been reviewed.

Baker, a former education secretary who chairs the Baker Dearing Trust, which promotes UTCs, accused EPI researchers of ignoring evidence.

“EPI start with their conclusion that a 14-18 institution cannot fit into an 11-18 system and then use statistics to support that,” he said.

“It is a pity that they did not take up Baker Dearing’s offer to visit several of our 50 UTCs and speak to teachers, students and parents.”

The EPI found many UTCs struggled to recruit students, and failed to retain the majority of those who did enrol. More than half of all UTC students left between the ages of 16 and 17 after taking GCSEs, while more continued to quit before finishing key stage five at the age of 18.

One in five UTCs were rated as inadequate by Ofsted inspectors, the EPI found, while a further 40% were rated as requiring improvement – well above the national average for mainstream schools in England.

Julian Gravatt, the deputy chief executive of the Association of Colleges, said the report showed UTCs “are an experiment that hasn’t worked”.

“Given the high level of support given to them by the DfE and the capital funding allocated by the Treasury, this is obviously depressing,” he said.

The analysis also found UTC students’ GCSE results were almost a grade lower than their peers at secondary schools. “Significantly, this poor progress is particularly acute for high attainers, who make over a grade’s less progress than high attainers in all state-funded schools,” the EPI noted.

The National Education Union said the report backed up its research, which found Black Country university technical college in Walsall cost more than £11m between its opening in 2011 and closure in 2015, with 158 students enrolled out of a planned 480.

Another UTC in Burnley cost £10m but closed three years after opening in 2013, with 113 students enrolled despite plans for 800.

The EPI did note several benefits from UTCs, including that they offer a wider range of technical subjects such as computer science than other schools.

The report concluded that existing UTCs should be repurposed as 16-18 colleges offering post-GCSE technical qualifications, such as the government’s promised T-levels.

But Gravatt said such a change needed careful consideration. “The 16-to-18 sector of education is already a chaotic and underfunded market,” he said.

A DfE spokesperson said UTCs were an important part of England’s diverse education system.