This Campbell systematic review assesses the overall impact on student achievement of processes and methods that are more student-centered versus less student-centered. It also considers the strength of student-centered practices in four teaching domains: (1) Flexibility: degree to which students can contribute to course design, selecting study materials and stating learning objectives; (2) Pacing of instruction: students can decide how fast to progress through course content and whether this progression is linear or iterative; (3) Teacher's role: ranging from authority figure and sole source of information, to teacher as equal partner in the learning process; and (4) Adaptability: degrees of manipulating learning environments, materials and activities to make them more student-centered. [This summary was based on the Campbell systematic review, "21st Century Adaptive Teaching and Individualized Learning Operationalized as Specific Blends of Student-Centered Instructional Events: A Systematic Review and Meta-Analysis" by Robert M. Bernard, Eugene Borokhovski, Richard F. Schmid, David I. Waddington and David I. Pickup.]