Understanding what contributes to improving a system will help us tackle the problems in education systems that usually fail disproportionately in providing quality education for all, especially for the most disadvantage sectors of the population. This paper presents the results of a qualitative systematic literature review aimed at providing a comprehensive overview of what education research can say about the factors that promote education systems' improvement. This literature is emerging as a topic of empirical research that merges comparative education and school effectiveness studies as standardized assessments make it possible to compare results across systems and time. To examine and synthesize the papers included in this review we followed a thematic analysis approach. We identify, analyze, and report patterns in the papers included in this systematic review. From the coding process, four drivers for system improvement emerged: (1) system-wide approaches; (2) human capital; (3) governance and macro-micro level bridges; and (4) availability of resources.