Enhancing social inclusion in young people could increase engagement in education, yet few longitudinal studies have examined this relationship. This study aimed to identify whether social inclusion in an Australian adolescent sample predicted high school completion three years later. Using state-representative data from the International Youth Development Study, two waves of the youngest cohort (51.6% female and 94.6% Australian born) during mid-adolescence (n = 825, Mage = 15.99, SD = 0.39) and post-secondary school (n = 809, Mage = 19.03, SD = 0.44) were analyzed. Factor analysis identified a 4-factor structure that represented an overarching social inclusion construct: (1) Citizenship, (2) Connectedness to Community, (3) Connectedness to Family, and (4) Connectedness to and Participation in School. Multivariate regression analyses indicated higher social inclusion levels in mid-adolescence predicted an increased likelihood of high school completion three years later. The implementation of strategies that incorporate the enhancement of social inclusion may improve educational outcomes for young people.