Bullying does not happen for any single reason. We have to look for causes in the culture, in the relations between the people around, and within the persons involved.

Because bullying happens between people, cultural norms and formal laws or rules in the country and school will have an impact on how much bullying will occur. Leadership in the school, and how well laws, rules and commitments to norms are observed are among the most important factors determining the level of bullying in a school or a society. 

The closer group of people - like the class in the school - also have a culture and a set of written / unwritten rules which they follow. Acceptance of harm-doing, exclusion, bad treatment or, on the other side: friendship, inclusion, are all determinants of the level of bullying in a class or a school.

We are not all alike as persons. Wetyher we like it or not, some of us are attracted to negative behaviors towards others. Some people - and also children - find it attractive to inflict pain onto others. Some have a strong appetite for control and power in social relations, and they may go beyond limits that we usually considder inappropriate.