Social and behavioral problems can interfere with a child's acquisition of age-appropriate skills, which may lead to antisocial behavior in adolescence and adulthood. Thus, determining how best to support positive skills during early childhood is critical. Using data from the first three phases of the NICHD Study of Early Child Care and Youth Development, I investigated whether participation in preschool, first, or third grade classrooms that were more emotionally supportive or academically focused resulted in better social skills and fewer problem behaviors at key transition points (i.e., preschool and third grade) than did participation in classrooms that were less supportive or less academically focused. Three findings are noteworthy. First, more emotionally supportive classrooms resulted in better social skills and fewer problem behaviors in preschool and third grade, even after correcting for observed family, child, and neighborhood selection factors; this effect did not exist for classrooms that were more academically focused. Second, immersion in classrooms that were more emotionally supportive at preschool, first, and third grade led to better social skills and fewer problem behaviors in preschool and third grade than did immersion in classrooms of average or below average emotional support across this period. Third, observed child factors, as opposed to family or neighborhood factors, seem to drive the pattern of findings. Effect sizes were small to modest. Implications for practice and future research are discussed. (Contains 2 tables and 4 figures.)