A confusing variety of terms is used in discussions of age grouping practices. This digest examines terms that have important implications for teaching and the curriculum. The terms "nongraded" and "ungraded" typically refer to grouping children in classes without grade-level designations and with more than a 1-year age span. The term "combined classes" refers to the inclusion of more than one grade level in a classroom. The term "continuous progress" generally implies that children remain with their classroom peers in an age cohort regardless of whether they have met prespecified grade-level achievement expectations. The terms "mixed-age" and "multi-age grouping" refer to grouping children so that the age span of the class is greater than 1 year, as in the nongraded or ungraded approach. These terms are used to emphasize the goal of using teaching practices that maximize the benefits of cooperation among children of various ages. The distinctions between the grouping practices have significant implications for practice. The ungraded approach acknowledges that age is a crude indicator of children's readiness to learn. Mixed-age grouping takes advantage of children's heterogeneous experiences. Research indicates that, in spite of its risks, the potential advantages of mixed-age grouping outweigh its disadvantages. (BC)