Bullying at school - Why is this a worldwide phenomenon?

I read an article by Daniel Goleman and he mentioned that bullying at school is a global phenomenon, present in virtually every country. He doesn’t explain the reason for it, but offers a wonderful method able to reduce bullying behavior significantly. It’s called

http://en.wikipedia.org/wiki/Jigsaw_Classroom

and the key ideas are the following:

Students of a normal-sized (26–33 students) class are broken into competency groups. Each group is given a list of subtopics to research, with individual members of the group breaking off to work with the “experts” of other groups, then returning to their starting body in the role of instructor for their subcategory.

The jigsaw teaching technique was invented and named in 1971 in Austin, Texas by a graduate professor named Elliot Aronson. Recent desegregation had forced a racial mix on the students of Austin, and many teachers were unable to cope with the turmoil and hostility of the situation. By arranging the students in culturally and racially diverse groups, Aronson and his team of graduate students were able to reduce the divisions between students. In fact, when one Hispanic boy named Carlos was tormented by his peers for his difficulty with the language, the bullying students were not admonished for their behavior. Instead, they were reminded that the exam was in fifteen minutes, and their sole source of information on the subject was Carlos, the boy they had been harassing. Behavior improved notably and immediately.

Due to desegregation, African-American, Caucasian, and Hispanic students were placed in the same classroom for the first time. In just a short time, there was an atmosphere of turmoil and hostility brought on by long-standing suspicion, distrust, and fear between groups. The superintendent of schools called Aronson and asked for his help. Aronson agreed only if he was allowed to look at the entire problem and give long-range solutions and not just temporary solutions that acted as a band-aid.

Do you know of any other methods which are effective against bullying? Societal norms are very different from country to country, but bullying behavior is very common. I remember this when I was in high school. What are the reasons? Is there a biological/genetic factor?