Mona Mourshed, Chinezi Chijioke, Michael Barber, via several kind readers:

“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.
Among other findings, the report shows that a school system can improve from any starting point and can become significantly more effective within six years. The research suggests that all improving systems implement similar sets of interventions to move from one particular performance level to the next, irrespective of culture, geography, politics, or history. A consistent cluster of interventions moves systems from poor to fair performance, a second cluster from fair to good performance, a third from good to great performance, and yet another from great to excellent performance. Although reaching each performance stage involves a common set of interventions, systems may sequence, time, and roll them out quite differently.