This study is designed on the basis on the key premises of Activity Theory, in the development of curriculum leadership among a group of primary teachers in two innovation engaged schools in Hong Kong China in April 2005 and 2007. Three curriculum development teams were formed and their membership and leadership were manipulated to create internal tensions and contradictions among members in a flattened leadership context. The aim is to investigate the extent that teacher participation in curriculum decision making processes is mediated by the artifacts such as hierarchical power, roles and leadership styles. The findings based on the analysis of the interviews as well as the video taped meetings of the Mathematics and Chinese curriculum teams point to the varying mediation effects of the two artifacts, namely the roles of the consultants and the leadership styles upon teacher participation. On the effects of the roles of the consultants, two types of professionality were asserting different influences on the mediation processes. The restricted professionality focused on closed discourse between participants and the leadership style was power coercive. The extended professionality however, generated an open discourse with evidence of multi-structural interaction pattern. The nature of the former is didactic while the latter is more negotiable among members. On leadership styles, the personality of the subject head and its degree of domination was having effects on the discourse styles and participation nature, though the distributed leadership was in function in the curriculum development teams. Assertive subject head constrained the interaction pattern of the meetings while the less assertive one opened opportunities for exploration and experimentation by the members of the teams. In conclusion, various artifacts assert their influences in the mediational processes of the interaction among members of the curriculum teams and these mediational effects have either constrained
