In a rapidly changing world, students' success depends upon the schools' capacity to deal with their specific instructional needs. Thus, effective teaching plays the role of a unique protective factor that may reduce and even close the achievement gap. Two broad questions structure this study: What is the research contribution to teacher quality and improvement? What elements of teacher quality support school improvement? As one driver of school improvement, teacher quality is especially pertinent for underperforming students, while school improvement is much more likely to emerge through collective capacity building. More specifically, I will argue that research-derived knowledge is key to ensuring both effective learning processes and whole school improvement.