Learning to teach within and across the settings of teacher education coursework and field experience in local schools is subject to the "two-worlds pitfall," where practices, norms, expectations, tools, and other aspects of teaching can be jarringly different. This remains an ever-present dilemma for preservice teachers, their teacher educators, and their school-based mentors. This collective case study follows two cohorts of secondary science teacher candidates (22 in total) through their field experiences in local schools to understand how they reorganized, repurposed, and retooled practice as they worked on noticing and responding to students using ambitious science teaching principles and practices. Analysis highlights how instructional experiences in K-12 classrooms and relationships with mentors afforded and constrained preservice teachers' efforts to recontextualize ambitious science teaching practices in the status quo science teaching contexts of local schools. Recommendations for increasing permeability between the two worlds of teacher preparation are included.