There are few studies exploring the impact and effectiveness of the science specialist model or its implementation specifically in urban schools. This ethnography explores the roles and responsibilities of science specialists in urban elementary schools, drawing upon interviews with the science specialists, classroom teachers, and building administrators to portray the science teaching identity and characteristics of the science specialists according to Social Identity Theory (Gee, 2000-2001) as well as classroom teacher science-teaching motivation, according to Expectancy Theory (Vroom, 1964). In this role, specialists provide science instruction, curriculum coordination and communication, and support of classroom teachers. The expectations and limits of leadership from the science specialist are also discussed. The use of science specialists to provide pull-out instruction, wherein a classroom teacher drops off her class for instruction by the specialist, results in a decreased sense of classroom teacher instrumentality. This model of science specialist instruction can also undercut other science teaching motivation components like expectancy of success, science-teaching identity, self efficacy and valence for science teaching. Science specialist instruction in a pull-out model can result in teacher disengagement from science instruction. Additionally, hierarchies flowing from school and district-level policy and practice are described and analyzed according to how they mediate and are mediated by a science specialist model.