This is the first of three chapters that draws on empirical, qualitative research data generated from an eight-month long ethnographic investigation of four teachers in an Australian secondary school setting. In particular, this chapter uses the knowledge and context frameworks outlined in Chap. 1 to examine the interplay between policy, micro-politics and digital practices in classroom settings. Considering the situated nature of teachers' workplace practices, this chapter illustrates how processes of communal membership--joint enterprise, shared repertoire and mutual engagement--and identity development--imagination, alignment and engagement--shape teachers interpretation of policy and subsequently the way their knowledge is enacted in their classrooms. Providing new elaborations to both the TPACK and communities of practice theoretical frames, this chapter concludes with evidence that processes of identity development and practice constitute aspects of context in which an individual enacts their TPACK in a communities of practice. [For chapter 1, "Contextualising the Use of Digital Technologies," see ED612246. For the complete volume, "Digital Technology, Schools and Teachers' Workplace Learning: Policy, Practice and Identity," see ED573988.]