This paper details the analysis of the participation of individual students in a teaching experiment in which the researcher aimed to facilitate a mathematical discourse community. This involved positioning students as mathematical authorities capable of generating and evaluating mathematical thinking. The extent to which students acted as mathematical authorities was investigated by tracking their participation across a number of lessons. Students' use of discourse community practices such as explaining and justifying thinking, evaluating the thinking of others and asking questions was documented and Wenger's (1998) trajectories of identity were used to describe their participation. The profiles of four students of different achievement levels with contrasting participation practices will be presented and discussed. [For the complete proceedings, see ED597799.]