Streaming is a divisive pedagogy in New Zealand due to the varied definitions of streaming, the ways streaming is perceived to influence the educational experience of young people, and the complexity of teaching students at a range of achievement levels. This article aims to gain an understanding of secondary school mathematics teachers' perspectives on streaming. Fifty-four secondary school mathematics teachers from across New Zealand were surveyed. The participants described a range of implications of streaming on their own practice, and a wide range of academic, affective and social implications of streaming on students, which showed that there is division amongst teachers around streaming. These implications often implied that teachers have narrow and homogeneous expectations of students in a streamed class. Further research could focus specifically on the homogeneous expectations of teachers in streamed classes.