This longitudinal study explores how one university's practice-based teacher preparation program prepared literacy teachers to develop practical knowledge for teaching and how that knowledge was tested and adapted in the first years of teaching. To understand change, we identified and analyzed points of tension, challenge, or dissonance in the first years, within and across activity systems. We draw on a cross-case analysis and examples from two single cases to explain our assertions that trying on models of practice and developing reflective routines allowed teachers to make strategic choices to accommodate and resist particular practices in their school contexts. Implications include designing practicum experiences to include opportunities to reflect on tensions between activity systems from University practical experiences through the first years.