Is entering into early childhood education (ECE) at a young age a resource or risk for language and social development? For the German National Education Panel Study – Newborn Cohort (analytical n = 2296), we balanced 23 covariates taken in infancy with inverse probability of treatment weighting (IPTW) and modeled relations between ECE entry age (very early entry <24, early entry 24-35, later entry >35 months) and societal language and social development age three to seven. Very early entry predicted larger vocabulary for dual language learners (DLLs) and children of less educated parents until first grade, implying “buffering effects.” Early entry also predicted vocabulary advantages in first grade. Very early and early entry predicted fewer peer problems until first grade. Very early entry predicted more prosocial behavior for monolinguals, but less for DLLs in first grade. Robustness checks suggested several of these advantages emerge only in diverse populations and revealed disadvantages implying “lost resources.”