The purpose of this qualitative descriptive study was to explore how special education teachers describe selecting and applying differentiated instructional strategies for students with mild, moderate, to severe disabilities in self-contained classrooms within a school district in Arizona. Jean Piaget's social constructivism theory and Carol Ann…

Background: Cluster-randomized experiments that assign intact groups such as schools or school districts to treatment conditions are increasingly common in educational research. Such experiments are inherently multilevel designs whose sensitivity (statistical power and precision of estimates) depends on the variance decomposition across levels.…