Does less mean more? Many pupils have been taught that 19th-century mill and mine owners feared cutting the length of the working week would reduce production, but often that was not the result.
It is a long way from the factory floor to the classroom but, as the map shows, the length of compulsory teaching time endured by 12 to 14-year-olds across the globe differs widely, from over 1,000 hours a year in the Netherlands and Italy, to less than 800 hours in Luxembourg, Finland and Sweden. That is a difference of around six weeks on a 35-hour week. Pupils in England study for 925 hours a year, or just over 24 hours a week without after-school activities. But that is without taking homework into account.
Some schools have tried to redefine the shape of the school day or the week in recent years with an end to the "two by four by eight" notion of education - that is, bounded by the two pages of a book, the four walls of a classroom and the eight periods of a typical secondary school day.
But more no doubt needs to be done to understand the relationship between learning and time intervals for effective study - after all, the average attention span of an adult is less than half an hour.
Then there is the debate about the long summer holiday and whether the break is a barrier to learning. Certainly, many of our practices, including the length of the school year, predate the present technological age. Might it be time for a review?
Of course, to those children in the developing world still denied education, any time in the classroom would represent a real gain.
John Howson is director of Education Data Surveys, part of TSL Education
NUMBER OF HOURS OF COMPULSORY TEACHING TIME AT AGES 12-14*