I argue that instructional coaches face inherent systemic conflicts when supporting standards-based reform. I interpret the politics of coaching as the local intermediation of broader debates about teacher accountability and teacher professionalism. Drawing on qualitative case study analysis, I examine the effects of macro-level ideological shifts in federal and state policy domains on coaches' implementation of district policy in one high-achieving school district from 2015-2016. I find that power over instructional expertise and access to teacher classrooms for observations were the most frequent sources of institutional tension. Despite these challenges, the coaches developed an instructional support system that promoted systemic reform and continuous improvement. Altogether, the implementation model devised by the coaching team, which leveraged cross-institutional social networks and collective knowledge pools, legitimizes the social origins of organizational improvement and innovation and fundamentally contradicts many of the prevailing beliefs imposed by accountability regimes. This study has implications for research on Network Improvement Communities (NICs), teacher professionalization, and systemic district reform.