Ability grouping has become increasingly common in the teaching of English in Swedish secondary schools. This study was concerned with the effects of different group constellations on the more able pupils. The research questions involved the able pupils’ performance, their roles in mixed-ability groups and whether the learning environment is better for them when they work with other able pupils. The study used discourse analysis of group interaction in the target language between pupils in year eight. It was found that able pupils perform according to their pre-defined skill, regardless of what groups they were put in. They also supported and lifted the interaction to higher levels in mixed-ability groups. Finally, the results suggested that able pupils might have a greater chance to develop their English in tracked groups. It is argued that this has implications for the implementation of ability grouping in the teaching of second languages in Sweden.