After Islamic revolution in IRAN, it was forbidden for men to teach in girls' schools and for women to teach in boys' schools. This religion-based approach was exactly to limit the opposite sexes' interaction in schools to prevent sexual abnormalities. There appeared, however, some conflicts in teaching affairs especially in elementary schools for 6 to 11 year-old students who were in close memory of mother at home, needing loving attention. Ironically, most students having come from kindergartens in which they were being taught along with the opposite sex were confronted a place free from their opposite sex counterpart. the governmental schools could not attract little children who came from kindergarten with women tutors as they felt they lost the motherhood love and attention. on the other hand, lack of social interaction with opposite sex in streets, parks or other public places led to the suppression of sexual instincts. This negative approach brought difficulties for university students when they saw the opposite sexes in university which reduced their academic abilities at least at entry level. the increasing number of university students who were forced to leave university or had loss of academic achievement shows that suppression of sexual instincts in youth can retard their growth and afflict them severely. the statistics of suicide among the youth are increasing. the focus of educational experts on establishing co-educational clubs has been a valve safety to help the youth to become adapted to the presence of opposite sex. This paper examines the psychological trends in separation of girls and boys.