Gender imbalance persists in developing countries in different fields. Education is one of the spaces in which gender imbalance continues to exist in Algeria, in terms of enrolment or achievement. This imbalance will unintentionally raise the issue of differentiation among genders at school. To this end, this research investigated the influence of gender differentiation on male pupils' success in secondary schools. The main objective was to examine to which extent gender bias could have an impact on learners' performance in foreign languages. As research instruments, a questionnaire and an observation were selected. Our sample is comprised of 131 pupils from Mosalaha and 80 pupils from Mohamed Boudhiaf Secondary Schools in the city of Tissemsilt- Algeria-. As for the observation, we have attended 10 English classes. The findings of this study revealed that differentiation exists in EFL classes and male pupils are threatened by the teachers' bias to females because of their number and interest in learning.