The director of one of the country’s biggest academy chains has warned that Progress 8 is biased “in favour of middle-class schools” and is costing school leaders their jobs.

Frank Norris, the head of the Co-op Academies, says that the GCSE performance measure - which is now one of the main ways in which secondaries are held to account - is “fundamentally flawed because it does not take a school’s context into account”.

He warned that this “simplistic analysis” by the Department for Education was costing some school leaders their jobs.

Now his trust plans to ask researchers to help produce its own contextual value added progress scores for parents to see alongside the official Progress 8 ratings.

Quick read: Strong link between Progress 8 and Ofsted rating

Exclusive: Progress score punishes schools in white working class areas 

Background: How does Progress 8 work?

The Co-op Academies Trust runs 20 schools in the North and Midlands including academies serving some of the country’s most deprived areas. It plans to take on another 20 schools by 2022.

Progress 8 is a performance measure used by the Department for Education which looks at how pupils have done across eight subjects over the course of their secondary education.

Tes revealed last year how a study by headteachers in the North revealed that Progress 8 penalises schools in disadvantaged areas that also have few pupils who speak English as an additional language.

Mr Norris said: “I am becoming more and more disillusioned with Progress 8 because I believe it is fundamentally flawed and biased towards schools with the most affluent intake.

“Despite our academies having the second lowest attainment on entry of any multi-academy trust in the country, our performance is strong, particularly for disadvantaged students. But this is not reflected fully in the Progress 8 analysis .”

He said that new research from the University of Bristol reveals if a contextual element is applied to the DfE’s performance data some schools would rise more than 500 places in the national league tables while others would fall by a similar amount.

Mr Norris added: “Some very good senior leaders have lost their jobs based on the DfE’s simplistic analysis and that is why it is imperative the data is as accurate as possible and takes into account every aspect of a school’s performance by applying a contextual element.

“Despite our academies having the second lowest attainment on entry of any multi-academy trust in the country our performance is strong particularly for disadvantaged students.

“But this is not reflected fully in the Progress 8 analysis. Without any contextual element, the data is flawed enabling schools in more economically and socially advantaged areas to appear to perform better.”

A Department for Education spokesperson said: “We want all pupils, whatever their background, to be able to fulfil their potential. That’s why we introduced Progress 8 as a fairer way to assess overall school effectiveness because it holds schools accountable for the performance of all of their pupils; not just those close to the C/D borderline.”

Mr Norris who was previously a senior HMI with Ofsted said he was involved in creating a school inspection framework that incorporated a contextual value added measure.

He added: “It was more sophisticated than the blunt Progress 8 measure we use today and in my opinion more reflective of a schools’ academic success but it was withdrawn by the DfE when the coalition government took over because it was believed that it didn’t challenge pupils sufficiently well to reach the national average.”

Dr George Leckie and Professor Harvey Goldstein at Bristol University’s School of Education have done research extending the Government’s Progress 8 measure to account not just for pupil prior attainment in English and maths, but pupil ethnicity, gender, age within year group, special educational needs and eligibility for free school meals.

Dr Leckie said: “When we look at these ‘adjusted Progress 8’ results for the Co-op’s academies, we see their ranking in the national school league tables rise considerably.

“The academies included in the research saw performance rise for three of them dramatically while one fell slightly. One of the academies rose by 24 percentile points to the 90th percentile.”

The Co-op Academies Trust is now considering asking the university to undertake a contextual value-added analysis for all of its academies each year and publicising this alongside the government figures.

Mr Norris added: “I would encourage other schools and trusts to do the same, so that parents and carers get a true picture of a school’s academic performance.”

Mr Norris is standing down as the director of Co-op Academies Trust at the end of this academic year.

The trust is carrying out major expansion plans and aims to run 40 schools by 2022.