Spare a thought for your US counterparts as you adjust back to school after the “long” summer break and try to deal with pupils who seem to have forgotten everything they learned last year. Most of them are returning after not six weeks but 10 and, in some cases, 12. Teenagers who have become accustomed to getting up in the afternoon spend the whole of September yawning through their 8am classes. Primary children adapt more quickly but are un-ruly for a fortnight.

If you are nevertheless tempted to envy the teachers such a long break, don’t be. The long summer imposes a relentless structure on the rest of the school year. My local district starts on September 1 and looks forward to just two, two-day breaks between then and Christmas. The Christmas break is only seven days and then there is just one week off (at Easter) between January 2 and June 13. As you can imagine, everyone burns out several times in the course of the year. You’re better off with a shorter summer and a school year punctuated with genuine breaks.

The explanation for the long summer vacation is what economists call path-dependency. Path-dependency is the phenomenon whereby an arrangement that once made good sense, but no longer does, survives because no-one can figure out how to change it. And the long summers did make sense when they were introduced.

The US established mass public schooling as early as the mid-19th century, when it was still mainly an agricultural economy. Parents wanted their children home to work on the farms in the long summers and were happy to have them out of the house in the winter when there was less to do. Most European countries, by contrast, established universal education only after they were already industrialised. In Britain, both the curriculum and the pace of the school year were modelled on the long-established, elite, boarding schools whose pupils were never expected to help bring in the harvest even if they did live on farms.

Now that only 2 per cent of the population is agricultural, it seems ludicrous to maintain a 19th century arrangement. But it is turning out to be hard to change. For once, my sympathies are with administrators, many of whom see the sense of having shorter summers and a more relaxed pace in the school year, but who often face resistance from teachers and parents. But the long summer has one advantage, and it is an advantage that will prove its downfall. Because summer is so long it is possible to study its effects on learning. And the results are very interesting. The preponderance of studies support the conclusion that whereas children from more advantaged backgrounds continue to learn throughout the summer, children from disadvantaged backgrounds fall back.

According to leading educational economist Richard Rothstein: “analyses of data from summer learning have often seemed to show that the entire growth in the gap, during the years children are in school, develops during summer vacation and so is probably attributable to out-of-school experiences. In these analyses, typical children from lower-class families seem to progress as rapidly during the school year as typical children from middle-class families, but the lower-class children fall behind in the summer, either because the middle-class children learn more or forget less in the summer months.”

Most readers will know that the gap in educational achievement between children from different social classes grows throughout the years of compulsory schooling. But what this research suggests is that the increase in the gap, like the initial gap, is not at all the fault of the schools, and entirely the fault of what goes on outside them.

Middle-class parents have the cultural and monetary resources to engage in summer and after-school activities which complement what goes on in school.

Working-class and poor parents, many of whom did not do well in school themselves, are less well positioned to reinforce the benefits of schooling.

Why will these findings result in summer being shortened? New national regulations insist that schools show annual year progress not just on average but for specific demographic groups, including children from low-income and ethnic minority homes. School districts will increasingly see that shortening the summer, especially for those groups, is the key to improving their achievement.

Several urban districts have already experimented, with modest, but measurable, improvements. National legislation, in other words, is finally providing the incentive needed to reform the school year.

Harry Brighouse is professor of philosophy and affiliate professor of education policy studies at Wisconsin university, Madison, US