When free schools were introduced, ministers said they would "drive up standards for all children", but the schools' first set of GCSE results appears to have fallen well below that expectation.
TES can reveal that at Robert Owen Academy in Hereford, only one pupil - representing 4 per cent of the GCSE cohort - achieved the government's basic benchmark of five or more A*-Cs including English and maths. And several other free schools have produced results that prominent supporters of the policy privately admit are "very alarming".
Among free schools that have released their statistics, two-thirds of newly formed schools failed to better the government's "floor standard" of 40 per cent of pupils achieving the GCSE benchmark (see panel, opposite). Meanwhile, all schools that had converted from independent status exceeded the target.
Even cheerleaders for the free schools programme now warn that it faces "hard questions", and it seems certain that the schools will be placed under much greater scrutiny.
A government source said that free schools with poor results were likely to have their Ofsted inspections brought forward. But they also pointed out that the schools represented only a tiny proportion of the programme. Just 18 of the 104 free schools that currently have key stage 4 pupils received GCSE results this summer.
According to a high-profile free school supporter, who wished to remain anonymous, officials would have been expecting underwhelming results from many of the schools as they were approved before tighter controls were brought in.
But they added that the lower-than-expected grades would lead to extra pressure on the 100 or so free schools with pupils taking GCSEs next summer.
"There's no getting away from the fact that these are a mixed bag of results, and some are very alarming," they said. "These results are totemic in a way, as they are the first proper results from free schools. It means there will be even greater scrutiny of free school results next year.
"You would be expecting the [Department for Education] to be asking some very hard questions."
Of the six newly formed free schools that released their results, only one - Bedford Free School - managed to do better, at 57 per cent, than last year's national state school average of 56.6 per cent of pupils achieving the main GCSE benchmark.
Robert Owen described its results as "disappointing" and other schools also posted underwhelming results. At Beccles Free School and Saxmundham Free School, both in Suffolk, just 39 per cent and 28 per cent of students respectively reached the benchmark. A third Suffolk school, IES Breckland, which is run by the profit-making Swedish firm Internationella Engelska Skolan, just hit the target with 40 per cent. It was placed into special measures by Ofsted last year.
Among the 12 newly formed free schools, half did not publish their GCSE results on their websites or respond to requests by TES for information.
Full national statistics have yet to be released, but Robert Owen's GCSE grades are likely to place it among the very lowest achievers in the country. The 14-19 school had a total of just 30 students on roll in 2014-15. It offers a "vocational baccalaureate", including a range of academic GCSEs, and aims to give pupils an alternative route into employment and training alongside "high academic expectations".
Since opening in September 2013, Robert Owen Academy has had three different principals, and in May was rated "inadequate" by Ofsted. In a statement, the school said: "[The] results, while disappointing, do represent success for a significant proportion of our students who have struggled in a number of educational settings for many years before joining the academy.
"The academy staff remain committed to further improvements and will continue to work with learners of all abilities to identify their needs and support them to achieve their potential and go on to play an active role in their community."
Early free school pioneers have already been hit by a series of high-profile problems. Last year, concerns over standards led to the closure of Discovery New School in West Sussex and the partial closure of Al-Madinah, a Muslim free school in Derby. And earlier this year, the Durham Free School was forced to shut its doors after inspectors rated it "inadequate".
The former Kings Science Academy in Bradford, which will receive its first GCSE results next year as the Dixons Kings Academy, was taken over by the Dixons Academies Trust in January after its founding headteacher was arrested for fraud.
Although many free school sixth forms secured good A-level results this year, the data released to TES reveals that in newly formed free schools an average of just 37 per cent of pupils achieved the government's main benchmark in GCSEs.
`Poor quality control'
Mary Bousted, general secretary of the ATL teaching union, said the free school results were "inevitable" and that children's education had suffered.
"What is abundantly clear is that the DfE did not have good quality control when it came to free schools, particularly in the early rounds," Dr Bousted said.
The New Schools Network, a government-funded charity that helps applicants to open free schools, said the programme was still in its early stages, adding that institutions such as the Bedford Free School - where 57 per cent of students achieved the benchmark - were improving standards.
"It is still relatively early days for the free schools programme, and many of the schools getting GCSE results this year have opened in areas with historically poor educational standards," the charity's director, Nick Timothy, said. "However, any school with disappointing results needs to work to turn around its performance - whether it is a free school or any other kind.
"It remains the case that free schools are more likely than other state schools to be judged outstanding by Ofsted."
A DfE spokesperson said that results were one of a number of factors on which schools' performance was judged, and free schools were providing "thousands of parents with more choice and are helping to drive up standards across the country".
But they added: "Underperformance at any school is unacceptable. One of the strengths of the free schools programme is that when we spot failure we can act quickly and decisively."
How free schools fared
Proportion of free school students achieving the GCSE benchmark of five A*-Cs including English and maths:
Newly formed free schools
Beccles Free School 39%
Bedford Free School 57%
Hadlow Rural Community School *
IES Breckland 40%
Maharishi Free School *
Robert Owen Academy 4%
Sandymoor School *
Saxmundham Free School 28%
St Michael's Catholic Secondary School *
Stour Valley Community School 54%
The Hawthorne's Free School *
The Rural Enterprise Academy *
Average of known figures 37%
Former independent schools
Batley Grammar School 70%
Bradford Girls' Grammar School *
Chetwynde School 80%
Holy Trinity School 85%
Queen Elizabeth's Grammar School 84%
Sandbach School 63%
Average of known figures 76%
* Results not released
Robert Owen Academy, where 4 per cent of students achieved the benchmark:
"[The] results, while disappointing, do represent success for a significant proportion of our students."
Seckford Foundation Free Schools Trust, which sponsors Beccles (39 per cent) and Saxmundham (28 per cent) free schools:
"[The trust is] disappointed with the overall statistics and recognises that it hasn't done as well as it wanted or expected to. However, the trust stresses that both schools have added considerable value to their students' education since opening in September 2012, and there are some fantastic results for individual students."
IES Breckland (40 per cent):
"Although this seems to be low, our students have achieved above expectations and the school has added considerable value to their outcomes, despite numerous challenges encountered."
The goal: `driving up standards for all'
When the first tranche of free schools was launched in 2011, then education secretary Michael Gove claimed that the programme was "spurred by a moral imperative" not to let another generation of children down.
The government, Mr Gove said, was in a "hurry" to open the free schools but would also be "uncompromising" when it came to quality. He also told the Commons Education Select Committee that free schools were "helping to drive up standards for all children, particularly the most disadvantaged".
The current education secretary Nicky Morgan has continued in the same vein. As recently as May, she said that they were at the "heart of the government's commitment to deliver real social justice by ensuring all pupils have access to a world-class education".