Head Start on Science is an early childhood science curriculum. Teachers in two Head Start classrooms were trained in the curriculum and their outcomes and the outcomes of children in their classrooms were compared to classrooms that did not receive the training. Child outcomes assessed included cognitive, social-emotional functioning, and language, as well as scientific reasoning; teacher outcomes included attitudes about science education and use of active learning strategies in teaching science activities. Although the overall classroom behaviors of the intervention and comparison teachers were similar, intervention teachers were more likely to use the strategies and intervention children displayed more advanced scientific reasoning.