In this article we explore an effort to rethink curricular decision-making with a group of public pre-K teachers working in a context of curriculum escalation and commitment to play-based pedagogy. Through a professional development program designed to support developmentally and culturally responsive early mathematics, we examine how teachers took up the idea of engaging in mathematics with 4-year-olds in a way that married content knowledge and home practices. We look specifically at three teachers as they negotiated our vision of responsive practice, using the notion of improvisation as a metaphor to understand how they took up this new role. We found that just having the knowledge about developmentally responsive practices, funds of knowledge, or early math was a first step but it was not enough. How teachers took up the elements of the professional development was contingent on their capacity to improvise in their teaching, responding to children’s resources and interests in authentic ways.