Knowledge of science content and the ability to translate knowledge into effective teaching is known as teachers' "content knowledge for teaching" (CKT). Teachers with developed CKT are able to more effectively determine instructional and assessment activities that will deepen K-12 students' scientific literacy. However, preservice teachers (PSTs) can have limited opportunities to develop CKT, and little is known about how to support PST CKT development in elementary science teacher preparation. In our work, we developed instructional materials (i.e., "CKT Packets") intended to support teacher educators (TEs) in developing elementary PSTs' CKT for one content area--matter and its interactions. We facilitated a professional learning community for TEs to support their learning how to implement the materials in their courses. We report on results from a mixed-methods study using a quasi-experimental cohort control design with a pretest and posttest to understand differences in PSTs' CKT (N = 250) in eight TEs' science classrooms. Nesting PSTs within their TEs' courses, and controlling for PSTs' prior CKT, engagement time on the assessments, prior coursework, and TE time-invariant effects, we found preliminary evidence that PSTs achieved greater CKT when TEs implemented more CKT Packets. Salient factors that we hypothesize influenced TEs' productive uses of CKT Packets included disruptions to courses/contexts, TEs' sources of motivation for implementing Packets, TEs' entry points for the alignment of curricular materials with existing topics and pedagogical course emphases, TEs' approaches for first-time use of curricular materials, and TEs' experiences with the instructional routines of the Packets. We bound our interpretation of results within limitations (e.g., small sample size, quasi-experimental design) and suggest avenues for new research. Throughout this article, we include implications for TEs, PSTs, educative curricula developers, and researchers working to improve science teaching and learning for students.