Michael Gove's school reforms received another body blow this week, with leading academics from the University of Oxford countering key points underlying the education secretary's sweeping overhaul of GCSEs.
The broadside against the case for change was made in an analysis of research evidence, which casts doubt on ministers' assertions that GCSEs have been "dumbed down", that England is underperforming on international measures and that the reformed GCSEs will improve standards.
The Oxford criticism is the latest high-profile challenge to Mr Gove's controversial reforms. Last month, 100 education academics warned that his national curriculum changes would damage standards by promoting "rote learning without understanding" but were dismissed by the education secretary as "bad academia".
This week, heads' leaders called on ministers to introduce policies that were based on research evidence rather than their own personal beliefs.
In February, when introducing plans for tougher new GCSEs from 2015, Mr Gove said: "These proposals will, I believe, achieve a swift and significant rise in standards, right across the country."
But in their report the Oxford University Centre for Educational Assessment academics caution: "Raising the level of demand in examinations will not in itself raise standards of achievement."
Their study also calls into question many of the claims made about existing GCSEs, stating that questions have not become easier.
In September, the original consultation on changing the exams said the plan was "to restore rigour and confidence to our examination system at age 16, which has been undermined by years of continued grade inflation".
Mr Gove said in the same month that the reforms were needed to tackle "dumbing down" in GCSEs. But the Oxford researchers conclude: "Evidence does not point to a general pattern of decline in cognitive demand of examination questions."
They found that evidence for grade inflation was "mixed" and could be caused by "legitimate" factors such as better teaching and greater student effort, as well as teaching to the test and falling exam standards.
Brian Lightman, general secretary of the Association of School and College Leaders, said: "I think we are seeing policy that is based on what ministers believe is right, rather than what the evidence says."
Mr Gove has also used England's relative global position to justify the changes, stating that: "while (GCSE) pass rates have soared we have fallen down the international education league tables".
But the Oxford research paper paints a different picture, noting that "international test scores for England show no decline" and that the country's Programme for International Student Assessment (Pisa) scores are generally close to average, matching its "average level of spending on education".
The academics add that England's scores on the four-yearly Trends in Mathematics and Science Study (Timss) showed "no decline" between 1995 and 2011, and that the latest study places it in the top 10 countries for maths.
Mr Gove's clashes with academia go back as far as last summer when three of the four academic experts he appointed to advise the national curriculum review publicly criticised the way the government was handling it. This week it emerged that the expert panel, whose views were largely rejected, cost taxpayers #163;287,619.
The education secretary has said that GCSEs need reforming to "raise aspirations". But the Oxford academics write that "most young people in England have high aspirations". They add that the proposed changes to GCSEs are "unlikely" to improve aspiration because they will raise demand, reduce resits and lead to "fewer routes to success".
The academics also dismissed claims that breaking down GCSEs into modules had made exams easier. Research showed that end-of-course exams led to a "narrowing of the curriculum" and rote learning, they added.
A Department for Education spokesperson said: "It is no good standing still while others race ahead ... There is a problem if grades rise year after year ... yet employers and universities say school-leavers are poorly prepared for the real world.
"We are transforming our exam system to get rid of an over-reliance on modules and coursework so that pupils can develop an in-depth and lasting understanding."
Research evidence relating to proposals for reform of the GCSE by Jo-Anne Baird, Ayesha Ahmed, Therese Hopfenbeck, Carol Brown and Victoria Elliott is available at bit.ly11909RO
I SPY IGCSE APPEAL
The number of state schools using IGCSEs has increased more than fivefold since 2011, figures released today show.
The sharp climb - from 166 schools in 2011 to 368 last year and 963 in 2013 - means that the state sector now accounts for nearly three-quarters of the 1,339 UK schools offering the Cambridge International Examinations version of the qualification.
Originally developed for the overseas market, the IGCSE has the linear, reduced coursework structure the government now intends to introduce for domestic GCSEs. Until 2012, the majority of UK schools using it were in the independent sector.
Sciences have experienced particularly large growth, with entries up from 3,797 last year to 8,689 in 2013, of which more than half - 4,716 - are in the state sector. The figures do not include IGCSEs offered by other boards such as Edexcel and AQA.
Source: Cambridge International Examinations.