Schools are an ideal setting for policy, systems, and environmental (PSE) approaches to childhood obesity prevention. An initial assessment of a school's health environment, policies, and practices is critical for planning and identifying priority PSE interventions, while reassessment can be used to identify measurable change for ongoing planning and evaluation purposes. School-based obesity prevention programs need an assessment that measures wellness policy implementation and compliance at the school level, as required by the Local School Wellness Policy Implementation Final Rule of the Healthy Hunger-Free Kids Act of 2010. The assessment must comprehensively assesses school nutrition and physical activity practices, and have the measurement properties necessary to detect change over time and differences between schools. Nutrition Policy Institute researchers shared the development and psychometric testing of a site-level questionnaire for elementary schools that fills this gap in an article published December 20, 2021 in the journal Childhood Obesity. Elementary schools and their partners can use the new instrument to plan PSE interventions, measure obesity-prevention best practices and wellness policy implementation, and evaluate their progress towards achieving best practices in nutrition and physical activity. Study authors include researchers from the NPI CalFresh Healthy Living evaluation team, Carolyn Rider, Janice Kao, Sridharshi Hewawitharana, Christina Becker, Amanda Linares, and Gail Woodward-Lopez.