What happens as beginning urban teachers transition through their first few years in the classroom? This book captures one teacher's journey through the first three years of teaching science and mathematics in a large urban district in the US. The authors focus on Ian's agency as a beginning teacher and explore his success in working with diverse students. Using critical ethnography combined with first-person narrative, they investigate Ian's teaching practices in four contexts: his student teaching experience, his work with students on a summer curriculum development project, his first year of teaching in a small, urban high school, and his second year of teaching in a large, comprehensive high school. In each field, the authors describe the structural changes Ian encounters and the ways in which he re-utilizes the practices he used successfully in previous fields. Specific practices that helped foster community and led to the increased agency of his students as learners are highlighted.