The long-term impact of children\u27s age at primary school entry on educational attainment and labor market outcomes is one of the primary concerns to families, educators, and policymakers. Using a nationally representative survey of families and individuals, this paper is among the first to explore these effects in a causal sense in the Chinese context and understand the underlying mechanisms. We use a regression discontinuity (RD) design that employs the threshold date for primary school entry set by the 1986 Compulsory Education Law of China as a source of exogenous variation in the timing of school entry. We first document a salient and robust compliance rate of school entry requirement. RD estimates indicate that being born right afte...