Immigrant and refugee children and adolescents form a growing socially, culturally, and economically diverse group with the potential for wide-ranging adaptation outcomes. The goal of the study was to examine whether developmental competencies (social-emotional and academic) and sociodemographic disparities (e.g., SES and migration class) identified in kindergarten forecast the academic achievement trajectories of first- and second-generation immigrant and refugee children, from childhood to adolescence. The study used a retrospective, longitudinal, population-based design by making use of linked, individual-level administrative data from four sources (e.g., Immigration, Refugees, and Citizenship Canada and Ministry of Education; IRCC, 2014 and BC MED, 2014) to identify a study cohort of immigrant and refugee children in British Columbia, Canada (N = 9,216). We utilized an analytical approach (group-based trajectory modeling) that allowed us to capture heterogeneity in the Grade 4 to Grade 10 academic (literacy and numeracy) trajectories. The resulting literacy and numeracy achievement trajectories were wide-ranging--some children thriving, some catching up, and some falling behind over time. Children's developmental competencies assessed in kindergarten (literacy, numeracy, and social-emotional) were found to predict later trajectory group membership in significant and, at times, interacting ways. Trajectory group membership also differed by migration class (refugee/immigrant), generation status, socioeconomic status, English language learner status, and sex. The findings highlight the need for early, targeted school and community interventions that will help set all immigrant and refugee children onto long-term paths of positive adaptation.