Aim: To evaluate the psychometric properties of a new measure of school belonging. Rationale: The sense of belonging to the school (organisation) as opposed to individuals within a school (peers) plays a significant part in pupils' behaviour and wellbeing. To date, few psychometrically robust, theoretically driven and brief scales exist. Consisting of only 12 items, the School Belonging Scale (SBS) was developed to assess three theoretically derived aspects of school belonging: attachment or bonding to school, acceptance of rules, and perceived school support. Method: A total of 3522 (42.9 per cent male) pupils in Years 7 to 11 from 6 metropolitan private schools in Sydney, Australia participated in the present study. Participants ranged from 11 years to 17 years of age (M=13.8, SD= 1.4). The data collected from the participants was used to assesses the SBS's reliability and Confirmatory Factor Analysis (CFA) was used to assess its factor structure. Additional tests of factorial invariance were also carried out to test the validity of the measure across boys and girls. Findings: Internal consistency estimates were very good to excellent. Results of the CFA indicated that all three factors were well defined. Invariance testing showed that the SBS is invariant across boys and girls. Limitations: Participants were from private schools; other limitations are discussed. Conclusions: The SBS is reliable and applicable to both males and female pupils. It can be used as a brief assessment for school belonging in research, intervention development, and evaluation.