A key goal of science learning today is to support students in posing and answering questions about phenomena that matter to them while establishing a need to grapple with disciplinary ideas and practices reflected in standards. To be successful in this endeavor, teachers need to learn to partner with students on the direction of their learning while remaining attentive to goals for learning reflected in standards. In this paper, we explore the idea that educators' developing knowledge of curricular purposes and structures can help support their enactment of instructional materials that help them balance these two goals. Our study draws on 36 teachers' experiences of learning to teach with instructional materials aligned to the Next Generation Science Standards as part of a field test that included multiple cycles of professional development workshops and enactments. Our findings illustrate how teachers' knowledge of curriculum can help them make sense of their own growth in teaching.