Mixed-ability grouping is widespread in primary schools and in several subject areas in secondary schools in England. Notwithstanding, there is scant research on mixed-ability grouping in the education literature, particularly in terms of its impact on students’ experiences. The research reported in this paper employs enactment theory to provide original insights into the diverse practices and complex contextual factors that shape students’ perceptions and experiences of mixed-ability grouping in physical education (PE). Enactment theory acknowledges that school decisions about grouping policy are impacted by wider education policy and other contextual influences, and that the expression of grouping policies in specific subjects and classrooms is navigated and negotiated by students as well as teachers. The paper draws on data from in-depth, semi-structured focus groups with 41 Year 10 (aged 14–15) students in a mixed-gender secondary school in England to explore the different ways in which students are positioned and position themselves in the enactment of mixed-ability grouping in PE. Findings reveal many contextual factors, including ability and gender discourses, school and subject cultures, and the broader policy context, influencing students’ positioning and learning experiences in mixed-ability PE. The discussion explores distinct differences in the enactment of mixed-ability grouping in PE in Key Stage 3 (aged 11–14) and Key Stage 4 (aged 14–16) and identifies students as enthusiasts, critics, entrepreneurs and copers in grouping policy enactment. The study affirms the need for educators and professionals to critically engage with the construct of ability, and in turn mixed-ability grouping policies and pedagogic practices in PE.