There are a number of ways used in bullying from mischief to delinquency but what is most inherent in bullying? The study analyzes the behavior and consciousness of Japanese elementary and junior high school students in the widely-disputed social problem-bullying. The analysis is focused on the fourfold structure in school system which encloses a student and at the same time reflects the social relations among students; peer group, class, grade and the whole school. The findings include (1) peer group and class are the main place where bullying is practiced; (2) when bullied, the victim children can hardly mobilize third parties like friends, teachers and parents to moderate the case; (3) in many cases, neither teachers nor parents recognaize bullying incidents. Moreover, classmates as witnesses of the case tries to keep distance from the case. The structure of school system explains the second and the third points. On one hand, students have to maintain social relations with peers. On the other hand, the fixed fourfold structure of school system functions to block the intervention of third parties into bullying incidents. Moreover, bullied students have no way to escape from the state of bullying, since the school system usually do not allow them to be replaced to another class, grade or school. As a consequence, the school system itself allows the maintenance of bullying in peer group and classroom. Consideration of the school system is duly encouraged in the discussion of bullying.