Abstract Adjusting speed to maintain fast and accurate performance is critical to goal-directed behavior. This study examined development of response time adjustments in the stop signal task in 13,709 individuals aged 6–17 years (49.0% Caucasian) across four trial types: correct and incorrect go, successful (stop-inhibit), and failed (stop-respond) trials. People sped more after correct than incorrect go responses and slowed more after failed than successful stop trials. Greater slowing after stop-respond but less slowing after stop-inhibit trials was associated with better response inhibition. Response time adjustments were evident in children as young as age 6, developed throughout childhood, and plateaued by age 10. Results were consistent with the predictions of the error detection and shifting goal priority hypotheses for adjustments.