This paper first identifies the different security measures and parental restrictions on children's playing activity in a number of elementary school districts. It then clarifies the cause of the difference by analyzing the environmental factors of each district. In districts which are crowded with high-rise condominiums and highways, and in which the alternative places for children to play are few, control is found to be stricter. It is also found that the increasing level of crime and the excessive information about it often makes the parents control the children's activities very carefully and their playing area very small and within a five-minutes walk from their homes.