Teaching pupils in classes grouped by ability improves the results of high-flyers but does not affect the progress of less able children, according to a study that upends decades of debate over mixed-ability education.

The research by University College London’s Institute of Education found that secondary school pupils in England with previously strong maths performances made slower progress in mixed-attainment classes than when they were taught alongside children with similarly high ability.

Crucially, the study backed by the Education Endowment Foundation (EEF) showed that setting by ability did not “significantly harm the attainment of low-prior-attaining or socioeconomically disadvantaged” pupils.

The study’s impact analysis showed negative effects on self-confidence in maths for pupils in mixed-attainment schools, compared with those in schools using setting – challenging previous reports that setting harms the confidence of those outside the top sets.

John Jerrim, professor of education and social…