What must a school system that performs poorly do to become good? And what must a system with good performance do to become excellent? In a new McKinsey report, How the world’s most improved school systems keep getting better, we attempt to answer these questions.

We analyzed 20 systems from around the world—all with improving but differing levels of performance—and examined how each has achieved significant, sustained, and widespread gains in student outcomes, as measured by international and national assessments. The report was based on more than 200 interviews with stakeholders in school systems and an analysis of some 600 interventions they carried out—two strands of research comprising what we believe is the most comprehensive database of global school system reform ever assembled. It identifies the reform elements replicable for school systems elsewhere, as well as those elements that are context specific, as they move from poor to fair to good to great to excellent performance.