Research Findings: National policy today is on the brink of defining preschool experiences as essential for children's academic success. Indeed, many children's classroom experience begins as they transition from infant/toddler care to a preschool classroom. This study examined developmentally relevant skill domains among 36-month-olds (effortful control, social engagement, and language abilities) and tested their organization in a latent factor model of skills hypothesized to promote classroom adaptation. Assessments of low-income children interacting with a parent and examiner from the Early Head Start Research and Evaluation Project were utilized (n = 1,814). The data included observations of mother-child interactions during semistructured activities at home and child behavior assessments. Results indicated that the interrelated structure of children's skills was best defined in a 2-factor, latent variable model: effortful control and social communication. These learning skills were related to but separate from general cognitive ability. Practice or Policy: Home-visiting programs for infants and toddlers are expected to promote children's school readiness, yet little research has focused on the skills that facilitate children's transition to the large-group learning environment at age 3. Implications of this model for early prevention efforts and early childhood teacher training to promote children's readiness for group-based learning are discussed.