The purposes of this study are to investigate the aspect of homosexuality as null curriculum in the religious education at school and to search a possible educational strategy for introducing sex education into the official curriculum. Two major contents through this study are as following: (1) what are the aspects of homosexuality as null curriculum in the religious education at school? (2) what could be the best strategy to bring homosexuality, presented in the religious education, as null curriculum into the formal curriculum? The results from this study are based on the literature survey, the data analyzed on the religious education presented in official curriculum and study plans. The interview results with religion teachers have been considered as well. The possible educational strategies of sex education, which can be presented as official education in the religious education, have been suggested.