Mrs Cooper undertook extensive research, some of it at The TES, but mostly at “schools of all kinds”. This, she told the Observer, was “a real eye-opener” because “I’d no idea that some children have nowhere to do homework, or that their parents are out of it on drugs”.

It would be unfair to pillory Mrs Cooper who, so far as I know, has never previously aired any views on education. If she has spent her life believing that everybody lives in large houses in the Cotswolds, as she and her husband do, that is her affair. At least when she started to write about education, albeit only in fictional form, she took the trouble to learn about it.

But I wonder how many of the commentators and politicians who influence public debate have similar lacunae in their knowledge. Take, for example, the Independent columnist Deborah Orr, who recently wrote of an unnamed school in the London borough of Lambeth, where she lives: “Last year 47 per cent of pupils had passed five GCSEs at A* to C grade. This . . . means that 53 per cent left the school functionally illiterate.”

The best that can be said for this statement is that it depends what you mean by illiterate. Again, it is unfair to pillory an individual; most of Ms Orr’s columns are excellent. She is not the only commentator who accuses schools of turning out illiterates without considering what is meant by the term. Most alarmingly, I have seen several pundits write, as though it were incontrovertible fact, that levels of literacy were higher in Victorian England.

This claim seems to have originated in AN Wilson’s book The Victorians, first published in 2002. There, Wilson writes that “literacy levels had risen to about 92 per cent in the nation at large” by the time of 1870 Education Act. He cites EG West: Education and the State as the source for his figures. When I sent for this book, it turned out to have been published by the Institute of Economic Affairs, a right-wing think-tank. Mr West was an economist, not an expert on educational history.

Mr West makes a plausible argument that literacy levels were higher in Victorian England. In the 1830s, even among criminals and workhouse children, literacy was around 40 per cent.

Among Northumberland and Durham miners in 1840, 445 out of 843 could both read and write. By 1870, according to the Registrar General’s figures, more than 80 per cent of adult males were literate, and by 1900, 97 per cent.

But for the Registrar General at least, a signature on a marriage register was sufficient evidence of literacy. We know little about how more advanced reading and writing skills were tested, though we can draw some conclusions from looking at exercises set by school inspectors in the late 19th century under the “payment by results” regime. From these, it is clear that, by the 1880s, high standards in basic skills were attained by at least three-quarters of the children. The skills tested, however, were narrow and mechanical; they would not be adequate for, or even relevant to, the 21st century.

Today’s is a more complex world, with entirely different requirements.

Victorian children needed to understand rods and perches; our children need to understand computers. I suspect that, if more critics were to immerse themselves in schools, as Jilly Cooper did, they too would make some surprising discoveries.