Researchers in California may have identified one reason why girls tend to do better than boys at school: because they’re born to be early birds.

The educational gender gap is a source of concern across the developed world. In the US, 57 per cent of undergraduate bachelor’s degrees go to women. In the UK, girls do significantly better at GCSE and are vastly more likely to go on to university than boys. This year, some 94,000 more girls than boys applied to British universities via Ucas.According to a recent paper by two economists from the University of California at Davis, girls’ disproportionate educational achievements may have something to do with the timing of the school day. Multiple sleep studies have found that boys are built to wake up later than girls, who also cope better with sleep deprivation.

In what is probably the first analysis of the relationship between gender sleep cycle differences and the educational performance gap, UC Davis researchers Lester Lusher and Vasil Yesenov write: “Given the widespread sentiment that overall students are not receiving enough sleep, these studies suggest that early school start times could be especially detrimental to boys.”

The study is based on data from an unusual experiment carried out between 2008 and 2014 in one Eastern European school district, where administrators decided to try starting school in the afternoons. Students would begin school at 7.30am for a month, and then at 1.30pm for the following month, alternating monthly from morning to afternoon throughout the school year.Everything else about the school experience remained constant, such as the ordering of classes and the teachers who taught them. Lusher and Yesenov analysed more than 240,000 grades given to middle and high school students for assignments during that time, and found that boys showed significant improvement when classes began in the afternoon.

While girls remained by far the better students, boys closed the grades gap by up to 16 per cent in the afternoon. The authors’ explanation? “Sleep studies suggest that boys have longer circadian periods, or ‘body clocks’, predisposing them to later bedtimes and morning wake-up times. Consequently, girls show a stronger inclination for activity earlier in the day than boys.”

In other words, girls are more likely to be morning people. Whether that means school ought to start in the afternoon is another matter.