Many secondary schools sort students into 'ability'-based classes, but research shows that streaming students by ability is inequitable and does not improve student academic results. There has been little qualitative research that considers students' experiences of streaming, with none that compares students' experiences in classes that are streamed against the same students' experiences in other classes that are mixed-ability. The research in this paper explains student experiences of differences between their streamed and mixed-ability classrooms, including the perceived influence on their educational outcomes. The study is unique because the results project the voices of 25 Grade 10 secondary school students from three Western Australian public schools, 19 of whom had recently experienced transitions between streamed and mixed-ability grouping contexts. The findings offer new knowledge that begins to explain how different class grouping strategies are experienced differently by students. Contrasts made by the students in their teachers' provision of learning opportunities, learning aspirations, and learning environments between streamed and mixed-ability classes are discussed. The findings highlight how educational outcomes were shaped by the schools' grouping choices and the associated differences in teachers' expectations and provision of opportunities to learn. The results are of interest to educators making decisions about ability-grouping practices.