| This study investigated 10 preschool teachers who learned to support their prekindergarteners' mathematical development in new ways through implementation of an innovative curriculum through the Berkeley Math Readiness Project (MRP). A pre-MRP questionnaire was used to investigate teachers' professional backgrounds, expectations for prekindergarten math learning, knowledge of kindergarten curricula, and previous math instructional practices. A post-MRP interview was used to explore teachers' retrospective reflections on their math instructional goals and practices before the MRP, their instructional decision-making, observations, interpretations, and experiences during the MRP, and their plans for further MRP development in the upcoming year.; Teachers' participation in the MRP helped them realize that their prekindergarteners were capable of learning more mathematics than they had previously thought. At the same time, MRP's innovative practices required them to take a more active role in supporting their students' learning and required extra time, preparation, and effort. Case study analyses revealed three distinct groups that distinguished teachers' plans for incorporating MRP-based practices into their classrooms: Adopters, Samplers, and Rejecters.; The interpretive approach used in the study identified the beliefs, values, and background knowledge that teachers brought to their MRP experiences, and the conditions under which teachers worked, as variables that seemed to shape teachers' appropriation of the MRP. Differences in teachers' understanding of what it means to know mathematics appeared to be related to their ability to focus on student conceptual understanding, foster a positive environment for math learning, and observe student mathematical growth, interest, confidence, and motivation. For some teachers, the experience of positive student outcomes consonant with their overarching goals and values helped offset the subjective experience of stress imposed by MRP. However, teachers serving low-income students faced greater challenges from greater time constraints and fewer material and personnel resources than teachers serving middle-income students. Practical implications for policy and professional development efforts, as well as recommendations for future research, are discussed. |