Expertise among teachers of students with extensive support needs is not well understood, and beliefs about what constitutes quality education for this population vary widely. We discuss findings from prior research on teacher preparation in relation to high-leverage practices and expertise development for students with extensive support needs within the social contexts of schools. We identify four core practices of expert teachers for students with extensive support needs, and we theorize the progression from novice to expert for each core practice using Dreyfus's (2004) model of expertise.