Relations between early problem behavior in preschool classrooms and a comprehensive set of school readiness outcomes were examined for a stratified random sample (N = 256) of 4-year-old children enrolled in a large, urban school district Head Start program. A series of multilevel models examined the unique contribution of early problem behavior in structured learning activities, peer interactions, and teacher interactions to reading, mathematics, and approaches to learning at the end of the year, accounting for child demographic variables (child age, sex, and ethnicity). Early problem behavior in structured learning activities consistently predicted lower academic outcomes (early reading and mathematics ability) as well as lower motivation, attention, and persistence in academically focused tasks. Early problem behavior in peer situations predicted lower attitude toward learning, reflecting children's difficulties self-regulating and engaging appropriately in socially mediated classroom learning activities. Implications for intervention within early childhood educational programs serving low-income children are discussed. (Contains 4 tables.)