Our schools still seem to be modelled on factories: preparing students in batches, using standardised procedures and punctuating the day with bells. This is an oft-repeated criticism of the education system, made most popular in recent years by the witty educationalist Sir Ken Robinson.
Actually, many aspects of the standard school day probably existed before the industrial era. The factory-model theory may be a bit like the belief that long summer holidays were invented so pupils could help their families bring in the harvest. (UK historians now believe the older public schools may have set the trends for holiday dates, and they were influenced by the timing of parliamentary recesses.)
But this should not detract from the argument. "We still educate children by batches," Sir Ken says. "We put them through the system by age group. Why do we do that? Why is there this assumption that the most important thing kids have in common is how old they are? It is like the most important thing about them is their date of manufacture."
Of course, schools educate pupils in year groups because it is practical. It also seems an improvement on what came before: the small single-classroom school with all ages shoved in together. That village school approach hardly seems conducive to personalised learning. However, the newer form of mixed-age schooling - vertical teaching and tutoring - can be.
Such was the excitement about "stage not age" teaching four years ago that Professor David Hargreaves, emeritus fellow of Wolfson College, Cambridge, made a bold prediction. He reckoned that by around 2013 the year group structure would have disappeared from schools in England. That prediction looks wildly optimistic now, but the trend to introduce some form of vertical learning is growing because of its many benefits.
A word of warning, though: the extreme version of "stage not age" education results in 16-year-olds being sent to university and infants sitting GCSEs. If education is a production line, then gifted and talented children sometimes deserve a bit of a rest on the conveyor belt.
Michael Shaw is editor of TESpro