Focusing on the science knowledge and pedagogical content knowledge that teachers need to realize the vision of the Next Generation Science Standards (NGSS) in their classrooms, this article presents findings from efforts to (a) adapt existing criteria and design heuristics for educative features of curriculum materials and apply them in the development of materials to support NGSS and (b) develop an authentic measure of teachers' knowledge and practice based on an analysis of teachers' evaluations of their students' written explanations of phenomena. The study demonstrates that existing criteria and heuristics for designing educative features of curriculum materials can be used productively, with minor modifications, to design features that support teachers in their use of materials that support NGSS. It also provides quantitative and qualitative data to show that teachers' analyses of the explanation task produced useful information about their understanding of the science ideas targeted in the assessment; of the misconceptions their students held; and of their students' ability to reason from evidence, science ideas, and models in explaining phenomena. This study builds on and contributes to a body of work on the design and use of educative curriculum materials and the evaluation of teacher knowledge. It suggests a practical approach to the design of NGSS-aligned curriculum materials that support both student and teacher learning based on findings from analysis and empirical studies.