The article reports data from an aspect of the study which aimed to study the nature of children's interactions and their perceptions of ability-based groups in a primary classroom in England. Previous studies on ability-based group have mainly used quantitative research designs to study children's interactions and appeared to award less opportunities to children to talk about their experiences of working in ability-based groups. This study has used qualitative ethnographic research design to study children's interactions and their perceptions of working in ability-based groups. Children's interactions were studied using participant observations and debriefing activities were used to elicit children's perspectives on their recorded interactions. Furthermore, informal conversational interviews were also used to hear children's perspectives on their experiences of working in ability-based groups. The article only focuses on data related to children's interactions, which revealed that children appeared to be cooperative, non-cooperative and competitive towards their peers in ability-based groups. We noted that children interpreted the group structure and learning task distinctively when deciding whether or not to work with others in groups. In some cases, children exhibited gender-biased attitudes while interacting with their peers. Children showed cooperative attitudes towards same-sex peers and non-cooperative attitudes towards other-sex peers. The findings highlight the importance of fully understanding children's contexts and their dynamic influences on children's interactions during their routinely organised ability-based group work. These also highlight the importance of listening to children's perspectives while studying their interactions in ability groups in the mainstream primary classrooms.