Among contemporary means of enhancing student learning, formative assessment is perhaps one of the most important and effective. While formative assessment ideas and practices have been shown to have a proven record enhancing student learning, these practices are slow to be fully integrated into teachers' day-to-day classroom practices. This study describes a collaborative effort among university faculty and public school partners to train teachers in the skills and practices of formative assessment. Regarding teachers' involvement in the formative assessment professional development, findings highlight that 1) teachers' participation in the professional development efforts did strengthen their understanding of both general knowledge of formative assessment and the use of formative assessment practices, 2) teachers' plans to use the strategies in the future were related to their understanding of these strategies, and 3) in-depth and comprehensive understanding of formative assessment practices were critical to concrete applications of such practices in their classrooms. With respect to the impact on student learning, an overall effect size of 0.41 was found for teachers who utilized a formative assessment strategy compared with district averages for similar learning objectives when the practices were not used.