This study tests the hypothesis that cultural differences in group orientation predict an interaction between the student variable--ethnicity--and a learning context variable--reward structure--on math performance after group learning. One hundred and thirty-two African-American and European-American female and male fourth and fifth grade students studied math estimation in one of three group learning contexts. The learning contexts operationalized were: intergroup competitive, interpersonally competitive, and communal-no reward. ANCOVA confirmed a predicted interaction of ethnicity with learning context on post study session performance. Although there was no difference overall, African-American and European-American students performed best in the aggregate in different contexts. Independent ratings of students' group-positive behaviors mirrored the two-way interaction between learning context and ethnicity. The findings suggest that important student variables interact with the variable elements of group learning and should be studied in greater detail. They also support Boykin's (1994) contention that the cultural context of learning is a critical mediator of children's achievement. (Contains 4 tables, 3 figures and 7 footnotes.)