The theoretical framework for analysis of classroom interaction extends the communicational perspective of Ognstad et al. (2005) and utilises the Joint Action Theory in Didactics of Sensevy (2011). This framework arises from an understanding of joint action a process of reciprocal semiosis involving the deciphering of verbal and bodily actions (or signs) of others in a particular situation. This process is seen to take place through didactic transactions in particular didactic settings that is conceptualised as a didactic game, as the core of the logical structure of the teaching-learning process. Key features of the joint action involved in this process are common ground, joint affordances, joint inferences and joint attention which will be used to help understand the joint didactic action of both teachers and students in the classroom setting. This paper will report on the findings of a classroom study based on the outcomes of a project funded by the Scottish Government (2010-12) with the aim of promoting the development of mathematical thinking in the primary classroom. Reference Ongstad, S., Hudson, B., Pepin, B., Imsen, G. and Kansanen, P. (2005) Didaktik and/in Mathematics Education. Studying a Discipline in International, Comparative and Communicational Perspectives. Oslo: Oslo University College, Norway.