This longitudinal multi-case study explored four early career teachers' attempts to differentiate instruction in schools that varied in their level of support for this pedagogical approach. It offered an in-depth examination of the experiences of novices who learned about the pedagogical tools of differentiation with depth and fidelity through the same preservice instruction, developed similar commitments to implementing them, and attempted to implement them in contrasting inservice settings. A large and rich data corpus collected across 4 years included participant interviews, observations of participants' teaching practices, classroom artifacts, and interviews with participants' mentors. Findings illustrated novices' contrasting multi-year learning trajectories related to differentiation embedded within varied school settings. They also revealed the substantive role novices' shifting visions of the enactment of practice played in appropriating differentiation's pedagogical tools during their early careers. Recommendations for teacher educators who prepare teacher candidates to differentiate are provided.

Within the lifetime of a significant segment of the population, schools in the United States operated under the banner of but equal opportunity. In time, and at considerable cost, we came to grips with the reality that separate is seldom equal. But half a century later, and with integration a given, many of our students still have separate and drastically unequal learning experiences (DarlingHammond, 2010). Many of our schools are overwhelmingly attended by low-income and racially and linguistically diverse students, whereas nearby schools are largely attended by students from more affluent and privileged backgrounds (Kozol, 2005). Another kind of separateness exists within schools. It's frequently the case that students attend classes that correlate highly with learners' race and socioeconomic status, with less privileged students in lower learning groups or tracks and more privileged students in more advanced ones (Darling-Hammond, 2010). The logic behind separating students by what educators perceive to be their ability is that it enables teachers to provide students with the kind of instruction they need. Teachers can remediate students who perform at a lower level of proficiency and accelerate those who perform at a higher level. All too often, however, students in lower-level classrooms receive a level of education that ensures they will remain at the tail end of the learning spectrum. Highend students may (or may not) experience rich and challenging learning opportunities, and students in the middle too often encounter uninspired learning experiences that may not be crippling but are seldom energizing. No group comes to know, understand, and value the others. Schools in which this arrangement is the norm often display an us versus them attitude that either defines the school environment or dwells just below the surface of daily exchanges.