This study evaluated the effectiveness of a gambling prevention program that aimed to correct the notions of chance and randomness among primary school students. The relative effectiveness of two prevention programs aiming to modify erroneous perceptions of gambling as well as the teacher's and specialist's on the psychology of gambling efficiencies to deliver the prevention programs were compared. Results showed that the program administered by a specialist of the psychology of gambling was more effective at decreasing erroneous perceptions than that provided by the teacher. The discussion raises the practical implications of these results for preventing gambling problems among primary school students, as well as the potential role that teachers could play in the implementation of such programs. (Contains 3 tables.)