In a sample of youth aged 10-16 years with chronic physical illness, this study examined psychometric properties of a modified Psychological Sense of School Membership (m-PSSM) scale; described longitudinal trends in perceptions over 24 months; and, identified factors associated with school belonging. Youth were recruited from a pediatric hospital in Canada. A total of 105 youth attended school in the past year and provided self-reports. The four-item m-PSSM had a unidimensional structure which was measurement invariant between youth in elementary (10-13 years) versus secondary school (14-16 years). Internal consistency was ([omega] > 0.80). There was no evidence that m-PSSM scores changed significantly over time ([eta] = 0.05). Predictors of lower perceived school belonging were being in secondary school, having psychopathology, reporting lower quality of life in the domains of social support and school environment, experiencing peer victimization, and living in a community with higher residential instability and lower material deprivation.