As the new school year approaches, most pupils in Detroit and New Orleans are preparing to return to desks in America’s charter schools. First permitted by Minnesota in 1991, charter schools are found in 43 states; in a few cities they have become mainstream. Academies — their equivalents in England — were set up later but have grown faster. Just 14 years after the first one opened in London, a quarter of all English state schools and two-thirds of secondaries are now academies.

These schools remain the great hope of education reformers in both countries and beyond. Though charters and academies differ in many ways, they were both conceived as alternatives to schools run directly by local governments. They are publicly funded but operated by charities or, in some American states, by companies. This model of public-private partnership has inspired several other countries including India, Kenya, Liberia, South Africa and Uganda.

International evidence suggests that schools do best when freed from government control. Competition from newly founded schools tends to raise others’ standards. But in both America and England, researchers have recently produced some troubling numbers. Although some charters and academies have achieved spectacular results, on average they appear to be little better than other schools when pupil characteristics are taken into account.

As a result, reformers are thinking afresh about autonomous schools. They are seeking ways to ensure that they are held to account, are well-led and that the exceptional teaching found in the best becomes the norm.

Before he was elected president, Barack Obama pledged to increase funding for charter schools. (There are still about 1 million children on charter waiting lists nationwide, and 23 of the 43 states that allow charter schools limit their growth). Race to the Top, a programme passed as part of the 2009 fiscal stimulus package, offered cash to areas that encouraged charters, introduced common standards and put measures to evaluate teachers in place.

The main motivation for creating the first group of academies in England was to raise standards for poor children, recalls Conor Ryan, an adviser to Tony Blair, the prime minister of the day. Many attended awful schools run by local authorities. So, in 2002, the Labour government said that failing schools would become academies, with more control over recruitment, timetabling and finances. When Labour left office in 2010 there were 200 such schools in England. (Scotland, Wales and Northern Ireland have distinct education systems, and no academies.)
Yet political enthusiasm seems to be waning on both sides of the Atlantic. Hillary Clinton is less keen on charters than President Obama. In England teachers, and even many Conservative MPs, fiercely opposed plans to increase academies. Theresa May, the new prime minister, has yet to comment on her plans for education.

The scepticism is partly a result of research suggesting that the impact of school autonomy is less impressive than advocates had hoped. A study in 2013 by the Centre for Research on Education Outcomes (CREDO) at Stanford University compared the results of pupils at charters with those of similar children in ordinary state schools. CREDO concluded that pupils in charters on average progressed by the equivalent of just eight additional days of learning per year (admittedly, many American charter schools get by on less money than other schools).

In England, academies are found at the top and bottom of the league tables that rank school success. As Lucy Heller, the chief executive of Ark, a charity that runs a successful group of academies, notes: “Autonomy provides a licence to do well, but also the freedom to do badly.”