Schools could improve pupils' maths performance without spending money on extra resources by scheduling lessons in the morning, according to new research.
But pupils are better equipped to tackle history in the afternoon, the findings suggest.
Scheduling mathematics classes in the morning and history classes in the afternoon results in higher test scores in those subjects, according to a study due to be presented at the Royal Economic Society's annual conference at the University of Bristol this week.
The study looked at variations in school timetables and monitored pupils' academic achievement and absence rates over nearly a decade.
It found that, when students took maths classes early in the day, they performed better than if they had studied the same class in the afternoon. The reverse was true of history.
Increase in performance
The research paper says the findings support existing research showing that performance in "repetitive, automatised or overlearnt tasks" is better early in the day, while "perpetual-restructuring tasks", such as making sense of history, are best kept for later.
The paper, written by Velichka Dimitrova of the Royal Holloway, University of London, concludes: "These results...present a low-cost intervention which can lead to an increase in student performance without substantial investments in school inputs."
The afternoon effect: differential impacts on student performance in maths and history is based on student-level term data spanning nine years, collected by a humanities high school in Bulgaria.
It follows research last month showing that delaying the school day would not help teenagers to get out of bed in the morning and that they would sleep better by turning down bright lights in the evening.