This study examined group differences by grade (fifth graders in elementary school and sixth graders in middle school) and gender in academic (behavioral and emotional engagement, academic self-concept, and worry) and socio-emotional adjustment (self-esteem, social satisfaction, social self-concept, and worry). Self-report data were collected from 1,003 students in the fall and spring of the school year (51.2% female, 36.7% Black, 47.2% White, 7.5% Hispanic, 5.7% Asian, 3% Other). Grade differences were null or favored fifth graders for academic adjustment. Grade differences were null or favored sixth graders for socio-emotional adjustment. Gender differences were null or favored girls for academic and socio-emotional adjustment; however, girls reported more worry in both domains. Change over time generally disfavored girls leading to the emergence of, or increases in, gender gaps by spring. The discussion considers early adolescent development and the need for continued attention to middle school reform regarding academic adjustment and gender differences.