Ability grouping is on the rise in American schools. Teachers engage in this classroom organizational strategy with the purpose of meeting individual learners' needs, improving student learning, and increasing test scores. However, there is opposition to ability grouping. Teachers who do not practice ability grouping often question its significance, believe it has a negative outcome on student achievement and self-concept, or prefer teaching whole-group instruction. This review of the research literature sought to determine the effectiveness of ability grouping on kindergarten through sixth grade students. Specifically, this review examined what ability grouping encompasses and the varying methods for implementing ability grouping at the elementary level. In addition, we investigated the effect of ability grouping on the academic achievement of advanced, on level, and below level elementary students. Finally, we explored how ability grouping influences the psychological and social welfare of young students.