The Psychological Sense of School Membership (PSSM) scale has been used for more than 20 years to measure students' sense of school belonging, yet its psychometric properties have had limited examination with pre-adolescent children. This study investigated the utility and psychometrics of the PSSM in three primary school samples from the United States, China, and the United Kingdom. Exploratory factor analysis revealed good fit for a unidimensional factor structure in the US sample, which was subsequently confirmed in all three samples. Partial invariance across all three samples and full invariance across pairwise samples (United States and United Kingdom; United Kingdom and China) was found. Path analyses revealed significant positive relations of the PSSM total belonging score with gratitude and prosocial behavior, and significant negative relations with symptoms of distress. Future directions and implications are discussed. [For the corresponding grantee submission, see ED588824.]