This study investigated the achievement and self-esteem effects of ability grouping of a cohort of Year 7 students in a small country secondary school. Intelligence was used as a control variable to determine whether ability grouping enhanced the academic performance of students. Results indicated that no inequitable spread of achievement benefit between high aptitude and mid-low aptitude groups occurred during the project. After eight months the differences between the groups on academic, general, home and social self-esteem subscales remained the same as at the beginning, although there was some non-significant evidence of a decrease in academic self-esteem in the mid-low aptitude groups. The academic self-esteem decrease was reflected in the general self-esteem of one of the mid-low aptitude groups but not in the other. The results were rather ambiguous with regard to academic self-esteem, with considerable variation occurring across the groups across different times.