Grade retention, the practice of requiring a student to remain in the same grade the following year, disproportionately affects students with sociodemographic risk and facing academic challenges. Each year, the United States spends $20 billion on retention and two million children are retained. Extant studies examining early elementary grade retention generally focus on short-term effects and academic outcomes; little is known about long-term effects on academic and psychosocial outcomes in the middle grades. The current study uses propensity score methods and a national data set to estimate the effect of first- or second-grade retention on academic achievement and psychosocial outcomes six or seven years later. By comparing students who were retained to students who were similar on observed characteristics but otherwise promoted, we generate causal estimates that show a statistically significant negative effect of retention on reading achievement. Significant and robust effects were not consistently detected for other academic or psychosocial outcomes. As grade retention is a widely used educational intervention, implications for its effectiveness from a policy and practice perspective are discussed.