Streaming in secondary schools is not beneficial for improving student outcomes of education with vast amounts of educational research indicating that it does not improve academic results and increases inequity. Yet teachers often prefer working in streamed classes, and research shows that teachers mediate the effects of streaming on students. This study sought to add to the understanding of teachers’ role in student learning by investigating how teachers conceptualise the students in streamed classes. A qualitative case study approach was used, where 18 teachers were interviewed in-depth to create narrative examples, three of which are presented here. These narratives summarise the research findings that teachers saw students in high and low streams as having homogenous characteristics according to five dichotomous categories: approach to learning, attitude to learning, learning style, autonomy and background. Students in mixed-ability classes were viewed along these same continua, but as more heterogeneous groups. Furthermore, these views of students had direct implications for how teachers planned for learning and the expectations that they held of their students. The discussion links streaming research with teacher expectation research, suggesting that teachers of streamed classes in this secondary school hold specific whole-class ideas that affect student learning. The article concludes with recommendations for further inquiry that links these two important fields of educational research.