Across the world, too few education policymakers have seen curriculum as a powerful lever for reforming schools. That might seem surprising. After all, “curriculum” is what we teach, and what we teach surely matters to student learning. As leading curriculum researcher Dr David Steiner of Johns Hopkins University in Baltimore puts it: “What we teach isn’t some side bar issue in American education: it is American education”.1 Yet for some years, curriculum has been overlooked as a pillar of school improvement strategy. Education reform has focused on teacher quality, and often seen curriculum as simply a tool that teachers use. Curriculum’s role as a battleground for ideologues has also led policymakers to avoid the subject. But that is beginning to change. The research is increasingly clear that quality curriculum matters to student achievement. What’s more, there is emerging evidence to suggest that quality curriculum has a larger cumulative impact on student achievement than many common school improvement interventions – and at a lower cost.