NATURE not nurture is the main determinant of how well children perform at school and university, according to a study to be published this week.

The researchers came to their conclusion by comparing how well adopted children did at school when they were brought up alongside parents’ biological children. The relative effects of genes and the home environment were then separated out.

Previous studies have suggested that the home environment, and in particular the level of family income, is the most important determinant of educational attainment.

But the new study, to be published in the Royal Economic Society’s Economic Journal, will argue that while income and home environment account for about 25% of educational attainment, inherited intelligence is responsible for the rest.

Doubling a family’s income would have only a small effect on educational performance, say the researchers, who examined more than 15,000 children, 574 of them adopted.

It found that on average the adopted children performed less well. This of course need not be a bar to success in life. Many adopted children, including Roman Abramovich, the Chelsea owner; Kate Adie, the BBC journalist; and Eric Clapton, the guitarist, enjoy spectacular careers.

The research may lead some to question policies such as the child tax credit and education maintenance allowances, which are aimed at improving the performance of poor children at school and university. Such policies, it suggests, will work only if targeted at able children.

The study, Does Family Income Matter for Schooling Outcomes? by Wim Vijverberg, professor of economics at Texas University, and Erik Plug, an economics researcher at Amsterdam University, concludes that previous studies suggesting a strong link between family income and educational performance were flawed.

“Children of higher income parents probably do well in school because they inherit superior genes, not because they can afford to buy their children a better education,” said Vijverberg.

Adoption experts said the research failed to take into consideration other factors. Jonathan Pearce, director of Adoption UK, said: “A lot of adopted children have faced previous trauma or abuse.”

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