The current paper reports long-term impacts of the Chicago School Readiness Project (CSRP) on measures of achievement, cognitive functioning, and behavioral regulation taken toward the end of students' high school careers. The CSRP was a self-regulation-focused early childhood intervention implemented in Head Start centers serving high-poverty neighborhoods in Chicago. The intervention was evaluated through a cluster randomized control trial, providing us with rare longitudinal evidence from an experimental study. However, the study was limited by issues with low power and baseline differences between experimental groups. Here, we report on follow-up data taken approximately 11-14 years after program completion, including measures of participants' (N = 430) academic achievement, executive functioning, emotional regulation, and behavioral problems, and we provide a range of analytic estimates to address the study's methodological concerns. Across our estimates, we found little evidence that the program had lasting impacts on indicators of late-adolescent functioning. Main effects were estimated with some imprecision, but nearly all models produced null effects across the broad array of outcomes considered. We also observed few indications that effects were moderated by posttreatment high school quality or later assignment to a light-touch mindset intervention. Implications for developmental theory and early childhood policy are discussed.