Researchers at Cardiff University have found that children who regularly eat a healthy breakfast are twice as likely to score highly in tests than those who do not eat before school.
The study of 5,000 nine-to-eleven-year-olds showed above average teacher assessment scores follow a healthy meal of items such as cereals, bread, fruit and milk products, with the one in five children whose breakfast consists of sweets and crisps seeing no academic benefit.
Lead researcher Hannah Littlecott said: "This study offers the strongest evidence yet of links between aspects of what pupils eat and how well they do at school."
Professor Chris Bonell of University College London added: "Many schools now offer their pupils a breakfast. Ensuring that those young people most in need benefit from these schemes may represent an important mechanism for boosting performance."