There is emerging evidence based on rigorous evaluations about how low-performing high schools can boost student achievement and keep students on track for graduation. This research brief, published by the National High School Center, draws on findings from four studies by MDRC that shed light on both the nature of the problems found in low-performing high schools and on the effectiveness of promising interventions that attempt to address those problems. Specifically, the lessons are based on evaluations of four high school reform models: Career Academies, First Things First, Project Graduation Really Achieves Dreams (GRAD), and Talent Development. These interventions were tested in 16 school districts.