Social inequality in achievement begins before children enter school and persists throughout schooling. The goal of the proposed research is to better understand the sources of these inequalities by examining higher order thinking (HOT), an important predictor of school success, in two types of children who are at risk for school failure: children at risk because they received inadequate linguistic input from their parents prior to school entry (environmental risk), and children at risk because they suffered unilateral focal brain injury prior to or at birth (organic risk). Our work builds on two longitudinal samples, 60 children selected to represent the demographics of the Chicago area, many of whom are experiencing low enough input to put them at risk for school failure, and 40 children who suffered pre- or perinatal brain injury, many of whom have lesions large enough to put them at risk for school failure. We have videotaped and transcribed parent-child talk at regular intervals in both samples from 14 months through 10 years, and will collect new data probing HOT at 11 and 12 years. Our goal is to determine whether early differences in parent HOT talk predict differences in child performance on tests of HOT in early adolescence. Having identified parent behaviors that set children on a trajectory toward the types of skills in HOT needed for school success, we will be in a better position to both encourage parents to use these behaviors and to construct materials and interventions designed to foster HOT, particularly for children who are at risk for not developing these skills without intervention.