This study used a person-centered approach to understand continuity and change in the externalizing behavior of children from economically disadvantaged families (N = 134). Groups of children differed in showing high levels of externalizing behavior in first grade (7 years old) that persisted (persistent problem) or decreased (improver) in third grade (9 years old) and low levels in first grade that were stable (unproblematic) or increased (new problem) in third grade. The results showed that verbal ability, behavioral impulsivity, parent maladjustment, and harsh parenting distinguished the persistent problem and unproblematic groups. Family instability was associated with change for the improver and new problem groups. The results suggest the importance of examining changes in the early adjustment to school for children from economically disadvantaged families.