“The foundational myth of the academies programme - that it would boost educational attainment among young people from disadvantaged backgrounds - must now be laid to rest as just that: a myth.”

There can be no doubting how the NEU teaching union joint-general secretary Mary Bousted feels about the revelation in Sutton Trust research that two-thirds of academy chains, also known as multi-academy trusts (MATs), perform below the national average for disadvantaged pupils.

It’s a shocking and potentially scary statistic. The Sutton Trust analysed the performance of disadvantaged students - those entitled to the pupil premium - in 2017, and over the five years of its Chain Effects series, the latest of which was published on Thursday.

Here are the key findings from the research:

• Some 38 MATs had attainment below the national mainstream average for disadvantaged pupils, including eight that were “well below average”.
• Twelve had above-average attainment for disadvantaged pupils, including three that were substantially above average: City of London, Diocese of London and the Harris Federation.
• There has been “only limited change” in the overall rankings over five years, with the same small group of chains consistently outperforming the national average, and another small group at the bottom each year.
• A small number of chains have shown consistent year-on-year improvement, “demonstrating that change is possible”.
• Chains that are most successful with disadvantaged pupils also tend to be successful with their more affluent pupils.
• The overall performance of disadvantaged pupils in sponsored academies became slightly worse between 2013 and 2016, but is now recovering.
• Sponsored academies have “performed very much better against the floor standard” since this measure moved from pupil attainment to pupil progress.
• Early results suggest that rebrokering academies “may be effective”.

But as with all such stories, there may be more to it than just the headline figures. Geoff Barton, general secretary of the Association of School and College Leaders, pointed out: “Different trusts will have different mixes of schools at different starting points. Securing sustainable improvement takes time and this is particularly challenging given that schools are inadequately funded by the government and face severe teacher shortages.”

And the Department for Education rejected the idea that academisation was a failure: “550,000 children study in sponsored primary and secondary academies that are now rated ‘good’ or ‘outstanding’...The latest key stage 2 performance data showed that disadvantaged pupils studying in MATs performed significantly better than the national average for disadvantaged pupils.”