AbstractThis paper will describe the way mathematical knowledge is presented and how it is understood by teachers and children in reception classroom contexts. Particular reference will be made to an exemplar, data handling lesson provided by each of the four teachers involved. The main focus will be placed on gathering and coding data and the patterns of interaction which emerged. Teacher and pupil interactions were recorded in four reception classes across children's first year at school. The emerging structure was one of co‐ordinating segments and subsegments which provided the ‘warp’ of lessons. Segments usually consisted of small group tasks and each had its own goals and actions. Analysis of lesson segments and subsegments into components, which carried implications for teacher and pupil actions, allowed access to recurrent patterns of teacher moves, or the ‘weft’ of lessons. Components comprised: introduction, tutoring and guiding, helping in task execution, monitoring and assessing, reviewing or commenting on results or outcomes. Not all segments contained all elements and individual teachers had their own distinctive styles of working. The amount of time in which there was opportunity to engage in mathematical tasks varied as well as the number of children involved and the quality of experience provided. Teacher talk and support varied from the irrelevant and goal‐free beset by management problems, through modelling, ‘talk aloud’ strategies with coaching and monitoring, to the more formal exposition with structured initiation‐response‐evaluation sequences. Rich teacher knowledge appeared to be reflected in the context and structure of lessons, in explicit and well‐integrated instruction, varied representations with links or connections made to existing skills and understanding. Results based on so small a sample of lessons, however, can be only suggestive of what a more extensive study of classroom