Mastery learning can be described as a set of group-based, individualized, teaching and learning strategies based on the premise that virtually all students can and will, in time, learn what the school has to teach. Inherent in this description are assumptions concerning the nature of schools, classroom instruction, and learners. According to the author, in mastery learning, both the teacher and learner are responsible for the desired learning. Moreover, differences in learning among individuals are, in fact, differences in the amount of time it takes them to learn. This amount of time is based upon three factors: his or her previous learning, his or her interest or confidence in learning the skill, and the quality of the instruction. Schooling is a purposeful activity, which should develop talent rather than select and categorize it. Instructional grouping practices often violate mastery learning's assumptions about individual students. (Author/MV)