The program team operating an NSF Noyce Master Teacher program has been building a conceptual framework for developing teacher leaders. The program has focused its efforts on a group of 16 chemistry and physics teachers in Southeast high-needs schools. The conceptual framework is based on the view that teacher leaders are those individuals who retain a classroom presence, while simultaneously innovating practice and empowering others. A core principle of the framework is that embodying these attributes requires an ability to see oneself and the teaching practice in a way that goes beyond the expertise associated with content and pedagogical knowledge. Evidence drawn from years three and four of the NSF Noyce Master Teacher program are presented to demonstrate the participating teachers' understanding of the framework's components. These data also indicate the potential of the teachers to use the framework's principles to engage in leadership activity. Characterizing such understanding and the changes in it are foundational to determining the way such a framework influences teachers' approaches to leadership. This paper has implications for the growing number of teacher leader initiatives across the United States, and for the question of whether science, technology, engineering, and mathematics (STEM) teacher leadership should be considered separately from a "general notion" of teacher leadership.