Ability grouping is a common practice among Hong Kong primary schools. This study examines the effect of ability grouping on students’ self-esteem, mood problems, and coping strategies. Eight hundred and ninety-two grades 3-6 primary school students completed a questionnaire that measured self-rated coping strategies, mood problems, and self-esteem. Students in high-ability classes showed higher self-esteem and reported using more emotion-oriented and problem-oriented coping strategies compared to students in regular classes. The differences in the use of emotion- and problem-oriented coping strategies or in self-esteem for high-ability versus regular classes were not attributable to differences in other variables, such as mood problems. Most of these ability-grouping effects disappeared after the students’ self-rated academic performance or conduct was taken into account. The impact of ability grouping on Hong Kong primary school students differs from those discussed in the literature, which could be accounted for by cultural factors, such as pride.