A running start

IN 1965 Lyndon Johnson introduced “Head Start” as part of his “War on Poverty”. Conceived as an intensive summer school for poor three- and four-year-olds, the programme now serves almost 1m children a year, all year round. That still leaves roughly half of American children of that age receiving no formal schooling at all, compared with just 10% or less in much of industrialised Europe and Asia—an imbalance politicians on the left, including Hillary Clinton, are eager to address. Not before time: research on early-childhood education suggests it is a smart investment.

By the time pupils begin primary school, there is a huge gap in achievement between rich and poor. In a 2011 paper Sean Reardon of Stanford University examined the difference in test scores in maths and reading between children from families in the 90th percentile of the income distribution and those in the 10th. He found that at age six it was already greater than one standard deviation and had barely diminished by the age of 18, leaving it equivalent to several extra years of secondary schooling. The gap was twice that between black and white students, and growing.