Background and Aim: Sex education of children, a complex issue in any culture, has always been a controversial subject. Schools can play a vital role in imparting sex education to children, particularly in more conservative communities. The objective of this study was to find out primary school teachers' beliefs, attitudes, values, and understandings regarding sex education of school pupils.

Materials and Methods: In this qualitative study we employed a community-based approach to design the project. Purposeful, voluntary and maximum variation sampling was used to recruit 22 teachers from selected schools in Western Tehran (21 female and 1 male teacher). Information was collected in 4 focus-group discussion sessions. Grounded theory and thematic analysis were used.

Results: Findings revealed three major themes: 1) organizational role, 2) institution construction, and 3) individual characteristics. These themes were described by subthemes as follows: 1. for organizational role: organizational culture and policies; 2. for institution construction: family and educational institutions; 3. for individual characteristics: biology, gender, instincts, curiosity, knowledge, and behaviors.

Conclusion: From the participants' point of views, the school and the family are two important institutions in children sex education. However, teachers are not sufficiently competent in sex behavior education. Inappropriate policies, resource limitations, and the family cultural structure are obstacles in sex education of children in schools. The participants believe the following are priorities in children's sex education: changing cultural attitudes in organizations and institutions, such as cultural diffusion; sound training approaches in sex-related topics; providing sufficient resources; improving knowledge and skills of teachers in the area of sex education of pupils; and effective interaction between families and school authorities.