Selective schools make no difference to pupils’ GCSE results, according to a scientific analysis that undercuts the argument that grammar schools are necessary for the brightest pupils to reach their full academic potential.
The study showed that the 7% difference in performance on GCSE results between selective schools (private and grammar) and comprehensives was almost entirely explained by differences in the ability and family income of the pupils. Once these factors were accounted for, the value added by selective schools dropped to less than 1%.
The study is also the first to show up subtle genetic differences between children who attend selective schools and those who do not. However, the genetic scoring system used to classify children in the study is viewed as controversial, and scientists are divided on the extent to which it is a true index for intelligence or academic potential.
The findings present a challenge to the government’s policy of allowing existing grammar schools to expand and open “satellite” campuses, and fuels an emerging debate about the role genetic testing should play in the future.
Prof Robert Plomin of King’s College London, senior author of the study, said: “It’s very surprising for people to find out that [selective] schools aren’t adding value. [The schools] take the kids that do the best at school and show they do the best at school. It’s an entirely self-fulfilling prophecy.”
The influence of genetics on achievement, Plomin suggested, is the “elephant in the classroom”, adding that in the future, genetic testing of children to predict their academic potential “will probably happen”. However, others questioned whether such a step would be useful or desirable.
In an added layer of controversy, the paper’s author list includes Toby Young, who stepped down from the Office for Students in January after critics highlighted offensive and sexist tweets, controversial writing about working-class students and an essay on “progressive eugenics” proposing that poorer people should be offered embryo screening based on intelligence. Young had been involved with the research for more than a year and made valuable contributions, Plomin said.
The study is not the first to undermine the claim that able pupils thrive in grammar schools, which has been widely used to justify the public funding of selective education. However, it is one of the first to look across all three school types – private, grammar and state non-selective – while also introducing genetics into the debate.
The study, based on 4,000 pupils who identified as white British and attended schools across the UK, assessed the pupils’ genetic data, their families’ socioeconomic status, their ability (measured by an IQ-style test), prior achievement (11+ or Sats results) and GCSE results.
Initially, school type appeared to explain about 7% of the differences seen in GCSE results (on average a grade difference in English, science or maths). However, after taking into account the selection factors, school type explained less than 1% of the differences seen in GCSE results.
“We’re showing if you took kids and randomly assigned them to schools, it wouldn’t make any difference,” said Plomin.
Scientists have been searching for more than a decade for “intelligence genes” that predict intellectual prowess, but no significant gene has been identified.
But by analysing data from hundreds of thousands of people, scientists have located thousands of DNA differences that each make a tiny statistical contribution to likelihood of academic success.
Even then, when these markers are totted up to give a so-called polygenic score, it only accounts for 8-9% of the differences between the GCSE results of pupils. And it is not yet clear what any of the genes represent – intelligence, diligence, competitiveness or even factors like having a strong bladder (helpful in exams) or a robust immune system.
The study found that, on average, three times as many students in the top 10% of polygenic scores went to a selective school compared with the bottom 10%, leading the authors to conclude that the British education system is “inadvertently selecting for genetic factors”.
Ewan Birney, director of the European Bioinformatics Institute, said the findings were in one sense unsurprising, given that almost any human trait has at least some genetic component – including educational attainment. However, he added that the paper did not score “an A+ on the statistics” and said that to be confident of the specific results, the claims needed to be tested more robustly.
Since grammar and private schools are geographically clustered, the paper also hinted at geographical variation in pupils’ polygenic scores.
Danny Dorling, a professor of geography at the University of Oxford, said: “For the authors’ interpretation of their findings to be true, the implication is that the large majority of children in the UK – who live and grow up in areas with no grammar schools and almost no private schools – have, on average, a genetic predisposition not to be that able.”
“The idea that private schools do not increase a child’s chance of being awarded more GCSEs and A-levels is not very credible,” he added.
Michael Reiss, professor of science education at University College London, said educators need to wake up to “the mounting weight of evidence” for genetics influencing school performance. “Faced with this legacy of sexism, racism and cultural imperialism, it is hardly surprising that educators, who by and large have liberal leanings and are in favour of social justice, have rejected genetics as a way of understanding what is important about humans,” he said. “What has happened is that genetics, rather than the misuse of genetics, has been rejected.”