This article first describes two studies previously published in English (Lyster, 2004; Lyster & Izquierdo, 2009) and then synthesizes their results to discuss how research setting and participants' age interact to differentially influence the effects of different types of corrective feedback. Both studies investigated the effects of form-focused instruction delivered in tandem with different types of corrective feedback on the acquisition of grammatical gender by classroom learners of French as a second language. Participants in Study 1 were eight classes of 179 French immersion students in Grade 5, while participants in Study 2 were two classes of 25 undergraduate students enrolled in a post-secondary intermediate-level French course. In both studies, classroom teachers provided form-focused instruction designed to draw attention to selected noun endings that reliably predict grammatical gender and also provided two different feedback treatments (recasts or prompts). Analyses of pretest, immediate-posttest, and delayed-posttest results showed a significant increase in the ability of students in both studies exposed to form-focused instruction to correctly assign grammatical gender. In the classroom study, however, child learners in French immersion classes benefited more from prompts than recasts, whereas in the lab study, university-level adult learners benefited equally from both prompts and recasts.