The shape and form of effective teacher-pupil talk has recently become the focus of attention within policy guidelines such as the National Numeracy and Literacy Strategies. Prior to this, research on classroom discourse has established that social context plays an important role in determining the quality of teacher-pupil talk since it directs teachers' and pupils' interpretations of what is said. This paper presents a multi-layered approach to the analysis of whole-class discussions which highlights the impact of wider, institutional and historical aspects of the classroom context on the meanings relayed within interactions. Video and audio data, collected over a five-month period of participant observation in a primary school mathematics classroom, highlights how issues such as teacher expectations and time pressure influence the quality of interactions pupils experience. The paper concludes that teacher-pupil interactions play an instrumental role in determining the social positioning of pupils within the classroom and this has a profound effect on the pupil's access to the learning process. In light of such findings, the potential limitations of establishing and implementing guidelines on effective teacher-pupil talk within policy are discussed.