Mastery Learning and Student Team Learning are two widely used instructional methods designed to confront the problem of student diversity in group-paced instruction. This study evaluated Mastery Learning, Student Team Learning, and a combination, in 43 inner-city math nine classes over a full school year. Results indicated greater achievement on a standardized test for Team classes than non-Team classes, but no greater achievement in Mastery than non-Mastery classes. Differences in time use were suggested to explain treatment differences in student achievement. (Author/MP)