Research has shown that teacher effectiveness is the most important school-based factor that influences student outcomes, including student achievement. Studies have also shown that there is substantial variation in teacher effectiveness, such that some teachers improve student outcomes at a much faster rate than others. The strong influence of teachers on student outcomes, as well as the variation in teacher effectiveness, has led to the creation of numerous programs designed to help teachers improve student outcomes. This review focuses on interventions aimed at making teachers more effective at improving the achievement of students in grades PK-12. These interventions are targeted at adults who are considering teaching; undergoing teacher preparation; or already employed in the teaching profession. The interventions may be delivered in a variety of educational and training settings. Although the interventions are delivered to teachers (or potential teachers), this review focuses on outcomes for both students and teachers. Student outcomes include measures of achievement, progression in school, social-emotional learning, and behavior. Teacher outcomes include those that research has shown are related to these student outcomes, including teacher retention and instructional practice.