Elementary students need to have meaningful experiences with the life sciences in order to develop understanding of the natural world. However, they often possess alternative ideas about core life-science concepts that may not be scientifically accurate. There is a need for innovative science curriculum and instruction that is responsive to students' ideas, to help students develop a foundation of disciplinary knowledge that will ground their science learning in later grades. Formative assessment gives teachers an important toolkit to elicit, evaluate, and respond to students' ideas. Formative-assessment practices are discipline-specific, in that they require teachers to possess both disciplinary content knowledge and sufficient pedagogical content knowledge (PCK). Unfortunately, formative-assessment practices are not widely used in elementary classrooms; this may be due to elementary teachers' limited disciplinary knowledge and PCK of science topics. Teachers need support in learning how to effectively engage in formative-assessment practices and to integrate the strategies into science classrooms. To address this need, we designed an innovative new course for prospective elementary teachers that integrates life-science disciplinary knowledge with instiuctional methods — in particular, formative assessment. Here, we describe the course and highlight key findings from its first implementation.