Earlier this year, a professional couple who I know in Washington – I shall call them Paul and Nancy – discovered they were about to become grandparents for the first time. They were overjoyed and rushed to prepare. But they did not merely buy a teddy for their spare room. Instead, they solemnly enrolled themselves into a so-called “grandparenting class”, run at a Jewish centre in Maryland. For several hours they sat in a classroom with a motley selection of new grandparents, mostly high-powered professionals in their sixties and seventies, and heard an ultra-enthusiastic teacher outline all the tricks of the new (old) grandparent game.

Welcome to the latest subtle twist in the fabric of modern American families – or at least some of the more wealthy and anxious ones. Back in the postwar years, when today’s babyboomer generation was born, charity groups and hospitals ran formal classes to teach parenting skills for new mothers. But nobody would have thought of teaching grandparents what to do: it was assumed that they knew the ropes since they’d had kids themselves. In any case, stay-at-home-mothers were the norm in the 1950s and, insofar as anyone was teaching anybody else about babies, it was the grandmother – not the mother – who was presumed to have the upper hand.

However, in the past decade, grandparenting classes have quietly mushroomed in middle-class urban centres such as Washington, New York, San Francisco and Seattle. Now they are spreading to places like London and Sydney too. This is not just heartening for anyone who wants to celebrate the role that grandparents can play in family life but a fascinating barometer of some wider social trends.