A large number of academies hailed as improving the chances of disadvantaged youths are consistently failing to deliver, a damning report has claimed.
The revelation is the latest story to highlight the obstacles facing the country's poorest students, after it was shown this week those wishing to go to university would face an extra £10,000 in debt because of the scrapping of maintenance grants.
Other measures hitting the demographic include the exclusion of under 25s from George Osborne's so-called 'living wage', as well as young jobseekers having housing benefit removed.
Almost half of schools analysed by education and social mobility think tank, the Sutton Trust, in its report on Friday were discovered to be performing below the Government's new 'coasting' level.
Education Secretary Nicky Morgan recently re-defined the 'coasting' threshold to include those schools consistently failing to ensure 60% of their pupils achieve five good GCSEs, including English and Maths.
But this week's research suggests poor children are performing significantly below last year's mainstream schools average in a third of academy chains.
The findings will marr the success of David Cameron's flagship education policy, which has been to drastically increase academy numbers and results attainment.
Commenting, Sutton Trust chairman Sir Peter Lampl said: "Many chain sponsors, despite several years in charge of their schools, continue to struggle to improve the outcomes of their most disadvantaged students."
He called on the Government to include a measure of attainment for disadvantaged pupils in its new criteria for coasting schools.
A Department for Education spokesman hit back at the criticism, saying: "It is wrong and misleading to try to classify coasting schools based on 2014 data alone. A coasting school can only be identified based on performance over three years, so we won't know until 2016 which schools they will be.
"The academies programme has transformed the lives of millions of pupils, particularly those from disadvantaged backgrounds, as this report shows. We are already working with many excellent academy sponsors and are recruiting more to pair with struggling schools so every child has access to the excellent education they deserve."
Tristram Hunt MP, Labour's shadow education secretary, rebutted: "David Cameron's first Education Bill of this parliament does not contain a single concrete measure for tackling under-performance in academy schools, despite the fact that more than half of all secondary schools are academies.
"The Tories think that the way to turn around under-performing schools is to simply turn them into academies and then walk away. They have no plan for those academies that are struggling, leaving them to fail or 'coast' and letting down the children who attend them."