While teacher effectiveness has been a particular focus of federal education policy, and districts allocate significant resources toward professional development for teachers, these efforts are guided by an unexplored assumption that classroom practice can be improved through intervention. Yet even assuming classroom practice is responsive, little information is available to inform stakeholder expectations about how much classroom practice may change through intervention, or whether particular aspects of classroom practice are more amenable to improvement. Moreover, a growing body of rigorous research evaluating programs with a focus on improving classroom practice provides a new opportunity to explore factors associated with changes in classroom practice, such as intervention, study sample, or contextual features. This study examines the question of responsiveness by conducting a meta-analysis of randomized experiments of interventions directed at classroom practice. Our empirical findings indicate that multiple dimensions of classroom practice improve meaningfully through classroom practice-directed intervention, on average, but also find substantial heterogeneity in the effects. Implications for practice and research are discussed.