This investigation examined patterns of codeveloping internalizing and externalizing problems from early childhood through adolescence (i.e., Grades 1 to 12). Subgroups of children with heterogeneous developmental trajectories (i.e., pure and co-occurring internalizing and externalizing problems) were identified and their long-term associations with teacher-child relationship quality and academic (math and reading) performance were assessed. Findings were based on a sample of 784 children (52.6% girls) who were followed from Grade 1 (M[subscript age] = 6.57) to Grade 12 (M[subscript age] = 17.57). Children's internalizing problems, externalizing problems, and teacher-child relationship quality were assessed annually from Grades 1 to 12, and their academic performance was assessed from Grades 1 to 9. Results revealed four distinct trajectories of internalizing and externalizing problems including chronic co-occurring, moderate co-occurring, pure-externalizing, and low-risk groups. Children with chronic co-occurring internalizing and externalizing problems exhibited more sustained teacher-child conflict, lower teacher-child warmth, and lower math and reading performance. Children with pure externalizing and moderate co-occurring problems were also at risk for scholastic difficulties, but to a lesser magnitude than children with chronic co-occurring problems. Compared to children in the low risk group, those in all three risk groups exhibited patterns of scholastic maladjustment that were either sustained or worsened after the transition to middle school.