Curriculum-based professional learning is not just having teachers read curriculum materials, but rather includes carefully crafted experiences to support their sensemaking, deep understanding of the curriculum and its pedagogy, and ability to transfer that knowledge into practice. This instructional model requires that teachers be responsive to their students and use their professional agency to craft a customized enactment of the curriculum materials. This article offers a vignette that comes from the curriculum-based professional learning designed by the authors and led for the OpenSciEd middle school curriculum. Engaging in high-quality curriculum-based professional learning over time that positions teachers as experts who need to customize the curriculum for their own classrooms can support teacher agency and key instructional shifts in science.