Teachers are regularly acknowledged as the single most important within school factor influencing student achievement. Yet, despite this claim, little is known about how teachers themselves understand high-stakes accountability in relation to their teaching practice. To study that relationship, this study asked how exemplary teachers' constructs of good teaching reside in a high-stakes accountability climate. The study was conducted in Maryland, during the first year of the restructuring of its previously high-stakes accountability system in response to the 2002 ratification of the No Child Left Behind Act. I employed an interpretive/descriptive case study methodology. Cases were developed on three mathematics teachers, two fifth grade teachers and one eighth grade teacher, who were selected by a panel of educational stakeholders within their individual school districts as Maryland Teacher of the Year candidates. Each teacher enacted a new mathematics curriculum, prepared their students for a new state achievement test, and responded to school based accountability driven structures and directives during the 2002-2003 school year. Data sources include classroom observations over an eight month period, interviews with the teachers and their principals, and artifacts from observations and interviews. Results indicated that the teachers' constructs of good teaching were based primarily on their beliefs about teaching as a moral endeavor with regard to their relationships with their students, the management of their classroom, and the way they represented mathematical knowledge and learning. Although each teacher addressed the well articulated academic achievement goals of Maryland's accountability policies in their practices, the 'principles' of accountability, the values, beliefs, and philosophies that underlie educational goals, were poorly expressed by the state making the teachers' constructs of good teaching sometimes at odds with official messages about accountable teaching. I concluded that although the teachers generally made significant efforts to enact accountability driven practices and work within prescribed curricular and school based structures aimed at improving instruction, the tensions between the teachers' principles of instructional accountability and the accountability messages they heard from the state must be mediated if instructional improvement in accordance with formal accountability goals are to take root.