This study tests the influence of a video-based, analysis-of-practice professional development (PD) program on upper-elementary teachers' science content knowledge, pedagogical content knowledge, and teaching practice and on their students' achievement. Using a cluster-randomized experimental design, the study compares the outcomes for teachers in an analysis-of-practice program with those of teachers in a content-deepening program. Mediational analyses explore the relationship between teacher outcomes and student learning. In comparison with the content-deepening PD program, the analysis-of-practice PD program significantly impacted teachers' knowledge and practice. Mediation analyses revealed a strong relationship between teaching practice and student learning. The study advances the field beyond the currently accepted consensus model of effective PD toward an empirically tested model.