Teachers' social interactions with children are a salient aspect of the classroom environment. An emerging line of research suggests teachers' emotional support consistency is an important predictor of children's academic and social outcomes. Yet individual differences determine the contribution of classroom affordances to children's adjustment. Adaptability describes a child's propensity to perceive and respond to changes in the social environment. Less adaptable children experience change as stressful and tend to be at risk for poor classroom functioning, perhaps more so in classrooms characterized by low levels of emotional support consistency. Multigroup analyses were performed in a structural equation modeling framework to assess the contribution of adaptability assessed in infancy to third-grade achievement and social skills in low- and high-consistency classrooms. Observations of 959 children in 805 third-grade classrooms, direct child assessment, and teacher ratings revealed that adaptability predicted a range of social skill and achievement measures in third-grade classrooms that offered low levels of emotional support consistency. Findings are situated in a goodness-of-fit model.