I wonder if we can trace this back to our Roots - Homo Sapiens was the first of the Homo genus to conquer the world. Up until then we scattered, retreated, etc. One theory of why we were able to do this is we developed superior weapons (advanced projectiles) and we co-operated with unrelated individuals because of our genetically determined propensity for this. [1]

Maybe this is why Facebook has over a Billion members?

Unfortunately TV and the Internet now has modified desire to co-operate extensively, creating, in my opinion, more self-centred'ness and much less of the Co-operation we had for most of our almost 3 million years as 'humans' on the planet.

Even considering only the time since we started the Agricultural period, we pursued Competition over Co-operation - aggression over pacifism, and I believe that is contributing to much of the Bullying we see today.

Recalling my Primary and Secondary school days, nothing like that I can recall in the lower grades and cliques certainly formed in High School, with perhaps an occasional temper flare, but no continual berating, name calling or bullying per say.
TV was new to the world in those days, and the Internet had many years to go before hatching.

[1] Curtis W. Marean - professor at the School of Human Evolution and Social Change at Arizona State U. and associate director of the Institute of Human Origins (ASU)