After the adoption of No Child Left Behind (NCLB), a host of anecdotal evidence suggested that NCLB diminished students' school engagement--a multidimensional construct that describes students' active involvement and commitment to school and encompasses students' thoughts, behaviors, and feelings about school. Using data from repeated cross-sections of the Children of the National Longitudinal Survey of Youth, this study draws on methodological innovations from research linking NCLB to academic outcomes to explore this possibility. Findings are suggestive of an immediate NCLB-based increase in engagement that diminished and ultimately became negative over time. Because engagement predicts both achievement and socio-emotional well-being, researchers and policymakers should work to ensure that the Every Student Succeeds Act facilitates accountability systems that promote engagement.