The new Every Student Succeeds Act offers states flexibility to create new approaches to school accountability and to design appropriate interventions for schools in need of assistance. The law states that the interventions should be "evidence-based" and defines the kinds of research evidence states need to provide when choosing strategies for improvement. This brief analyzes the research base and identifies the conditions under which four commonly used interventions have been found to be effective when well-implemented. The four areas are: high-quality professional development, class-size reduction, community schools and wraparound services, and high school redesign.