Two studies investigated the effects of parents' control and autonomy support on low- and high-achieving children. In Study 1, mothers' (N1=10) involvement with children (7 to 10 years old) in the context of a challenging task was observed. During this interaction, mothers' control predicted diminished engagement and their autonomy support predicted enhanced performance for low-achieving children more than for high-achieving children. In Study 2, mothers' (N1=21) responses to children's (9 to 12 years old) failure were assessed with a daily checklist. Children's grades were obtained at this time and 6 months later. Mothers' controlling responses predicted decreased performance and their autonomy-supportive responses predicted increased performance over time for low achievers more than for high achievers.