The purpose of this study was to explore aspects of sex education on the application of Islamic elementary school which the female students' classrooms and male students' classrooms are separated. The research method used was qualitative research. The researcher was the primer instrument, but the researcher needed the other's instruments. Therefore, additional data collection techniques used were interviewing and observing. The kind of interviewing technique was used in this research was the in-depth interview. Participant observation passively was selected to observe the subject and object of the research as additional data collection technique. The results suggest that sex education can be applied early and realized through the concept of school implanted is the existence of separate classes. Thus, separation of classes by gender based on the aspect of religiosity is very influential to sex education and characters education. Sex education can be applied to an early age and manifested through the concept of a school planted that is the existence of separate classes.