This is an innovative study that adds to our knowledge of classroom practices in Singapore schools. It counters the rather simplistic notion that the IRF pattern of discourse in classroom interaction necessarily means less effective teaching, by completing a detailed analysis of variations in function of the Follow up part of the pattern, and how this relates to the two different streams considered. This study, which is based on contemporary and comprehensive Singapore classroom data, is worthwhile and very timely, offering as it does valuable findings urgently needed in the context of the recent public debates about the effectiveness of streamed instruction in Singapore schools, and of governmental modifications, however minor, to the way ability grouping is determined, in order to allow for less qualitatively stratified teaching and learning.