In our study, we examine the factors influencing the implementation of a mathematics coaching initiative at four high schools including the assets an instructional coach brings to the position and the challenges unique to each school. In our case study we include data collected in individual interviews with instructional coaches, focus groups with Algebra I teams, and coaching logs. Four models of coaching behavior emerged from the data collected in the study: coach as facilitator, coach as mediator, coach as dictator, and coach as victim. No role was associated exclusively with any particular instructional coach. However, which role the coach assumed hinged on one or more factors: the coach's leadership style, the context in which the coach served, and the dynamics of the situation.