Research Findings: This article focuses on preschool science, an important but underresearched school readiness domain. There is considerable activity surrounding quality science in early childhood classroom practices, including state standards, curricula with science activities, and an extensive literature on potential best practices. However, there is very little empirical research focused on the effectiveness of these practices. The present article presents preliminary investigative research, a necessary first step in pursuing a research area that has been underexplored. The first study uses a large, ethnically diverse statewide database of Head Start children's school readiness to show that children end their pre-kindergarten year with science readiness scores significantly lower than readiness scores in all other measured domains. The second study identifies low self-efficacy in science and time-management issues as two possible barriers for why preschool teachers may have difficulty teaching science. The third study reports on a program designed to integrate other readiness domains around science activities, with promising results for children's school readiness in multiple domains. Practice or Policy: The article concludes with a discussion of future directions, emphasizing the need to focus on science in preschool classrooms and the critical role that science education can potentially play in improving early childhood classroom practices and child outcomes.

Young children are able to benefit from early science teaching but many preschool teachers have not had opportunities to deepen their own understanding of science or to develop their pedagogical content knowledge (PCK) in relation to specific science topics and concepts. This study presents the results of efficacy research on Foundations of Science Literacy (FSL), a comprehensive professional development program designed to support teachers’ knowledge of early childhood science; their PCK around 2 physical science topics (water, and balls and ramps); and their abilities to plan, facilitate, and assess young children’s learning during inquiry-based science explorations. Research Findings: In a randomized trial with 142 preschool teachers and 1,004 4-year-old children, FSL teachers demonstrated significantly higher quality science teaching in general and greater PCK in the 2 physical science topics than did teachers in comparison classrooms. Furthermore, children in FSL classrooms performed significantly better than children in comparison classrooms on tasks involving floating and sinking, and an instrumental variable analysis suggests that the quality of classroom science instruction mediated the relationship between teacher participation in FSL and student outcomes. Practice or Policy: Findings support the use of comprehensive early science professional development programs designed to bolster teacher knowledge and PCK.

High-quality instructional interaction, in which teachers engage children in conversations that support the development of higher order thinking skills, conceptual understanding, and advanced language skills, is associated with positive outcomes for preschool children. Classrooms serving low-income preschoolers tend to have lower levels of this kind of instruction and yet research suggests that it may be particularly important for these children. The aim of this study was to examine variation in the quality of instructional interactions in Head Start classrooms across different types of teacher-directed activities. Twenty-four Head Start classrooms were observed across four activity types (circle time, math activities, science activities, and storybook reading), and quality of instructional interaction was assessed using the Instructional Support domain of the Classroom Assessment Scoring System. Science activities and storybook reading were associated with higher quality instructional interaction compared with circle time, controlling for teacher characteristics and classroom contextual factors. Math activities were not associated with higher quality instructional interaction compared with circle time. Science and storybook reading may be natural entry points for supporting higher quality instructional interaction in Head Start classrooms.