Can teenagers' self-efficacy be improved in a short time? Previous research has shown the positive effect of cooperative learning methods, including "jigsaw classrooms" (Aronson and Patnoe, 1997), on various outcomes (e.g., the liking of school, self-esteem, and reduction of prejudices). The present practice report investigated the effects of jigsaw technique in boosting the self-efficacy of students enrolled in a vocational curriculum. Over a period of four sessions, 33 male participants studied school materials either in jigsaw groups or in a traditional class (individual work). Their academic self-efficacy in math and French was measured before and after treatment. Results indicated that students' self-efficacy increased after the four sessions, but only in the jigsaw group. This report provides additional evidence supporting the benefit of jigsaw classrooms based on a different outcome than the one used in previous research--namely, self-efficacy--and among a particular population--namely, vocational trainees. Implications for classroom practice are discussed. In particular, the present practice report demonstrates that implementing the jigsaw approach in classrooms might be an effective tool for enhancing the quality of vocational students' school experience.