This small scale study examined gender differences in self-efficacy. 24 girls and 28 boys aged between 10 and 12 years completed self-efficacy questionnaires and attainment tests. The study was conducted in two primary school classrooms in England and the results indicated that gender differences in self-efficacy were significant with boys holding a lower sense of self-efficacy than girls coupled with lower performance. Boys’ self-efficacy scores were significantly correlated with performance but this relationship was lower than that of the girls. Interviews with the two teachers involved in this study showed a lack of understanding and awareness of the self-efficacy beliefs of their students and the impact it potentially had on their students’ performance. Implications for teachers are discussed.