This paper addresses the current resurgence of interest in classroom talk and its place in pedagogy; in particular the role of teachers in shaping students' learning through the design of classroom interactivity. The importance of teacher agency with respect to pedagogic design is highlighted in recent studies of pedagogy in the UK (Alexander, 2008; Mercer, 2008) and in linguistically oriented studies of pedagogic discourse undertaken in the Australian context (Christie, 2002; Jones, 2005). The paper presents a case study of classroom talk to explore how such work might be brought into alignment in order to shed further light on the construction of educational meanings through oral language. In doing so, the importance of understanding pedagogy as the dynamic construction of learning contexts through interaction and over time is highlighted. (Contains 4 tables, 3 figures and 8 footnotes.)