The Flipped Classroom design has arguably revolutionized teaching across the globe. In this article we report the first comprehensive meta-analysis of its effects on student performance, relative to traditional teaching models, across disciplines and education level. We included 198 studies comprising 33,678 students in our meta-analysis. There were 174 studies conducted at the tertiary level, 21 at secondary, and three at primary school level. Overall, the flipped classroom had a moderate positive effect (g = .50) on student performance. The flipped classroom was beneficial regardless of discipline, with effect sizes ranging from weak (i.e., for IT, g = 0.30; k = 14) to strong (i.e., for humanities, g = 0.98; k = 34). Testing of other moderators relating to group sizes, in-class activities, pre-class testing, and the sophistication of a flipped classroom design provide evidence to suggest that the primary contributing factor to the flipped classroom effect is the opportunity it provides for structured, active learning and problem-solving.