This article focuses on the process of gender identity construction through the educational system from a socio-cultural perspective. Socialisation operates as a strategy to protect social unity and group superiority. Although socialisation is an enduring process involving various institutions, childhood is a vital period of gender socialisation whereby schools and school textbooks play a substantial role as the first official sources of socialisation in children. Using content analysis method, this article focuses on Iran's primary school textbooks. The results support the pattern of 'gender bias', rather than 'gender fairness'. This is a more evident observation in the higher educational grades. The patterns highlighted here are evidently incompatible with socio-demographic progresses in women's status over recent years, which call for revision in the school education resources in this context.