JJ, can we safely assume that you're male?

Most bullying is not of the 'physical assault' variety. It's endless little insults and social aggression. When the wealthy popular kid tells a poorer and more timid classmate, "I wouldn't ever want to play with you -- you aren't even dressed right"), that's bullying. It may be an honest sentiment, and it may be "natural" for kids to compete for social standing, but these ham-fisted demonstrations of having more social power than virtues are not positive social behaviors.

One of the major points that the article makes is that the response by bystanders to these displays really matters. If the other kids would stop nodding at this display of power, and start saying "Hey, she's a nice person, and it's not her fault that her parents don't have any money, and what you said isn't very kind", then the kid with the social power will be less inclined to pick on the victim (and will have to find other ways to signal social standing, such as displaying material wealth, or courting public signs of acceptance and respect from favored adults).