Maybe the problem is not related to size of the school but only related to the fact that kids have no choice in going there?
In the adult world, in most cases you aren't forced to go anywhere and only do so because you have a good reason, whether it's the workplace (earning money), universities (learning things because you need that knowledge), etc. Most people go into an establishment with a goal in mind, work towards that goal and have little time nor motivation for things like bullying.
School is different because kids have no say in the matter, so even if they aren't interested in learning (because the coursework is boring, irrelevant, etc) have to go there and waste ~8 hours a day and need to occupy themselves. Typical sources of entertainment (television, video games, etc) are forbidden so bullying, or similar anti-social activities happens to fill the gap. This results in a lose-lose situation; kids that aren't interested in the coursework are having a miserable time and entertain themselves by making the environment miserable for everyone else (both other pupils as well as the school staff).
In the adult world, in most cases you aren't forced to go anywhere and only do so because you have a good reason, whether it's the workplace (earning money), universities (learning things because you need that knowledge), etc. Most people go into an establishment with a goal in mind, work towards that goal and have little time nor motivation for things like bullying.
School is different because kids have no say in the matter, so even if they aren't interested in learning (because the coursework is boring, irrelevant, etc) have to go there and waste ~8 hours a day and need to occupy themselves. Typical sources of entertainment (television, video games, etc) are forbidden so bullying, or similar anti-social activities happens to fill the gap. This results in a lose-lose situation; kids that aren't interested in the coursework are having a miserable time and entertain themselves by making the environment miserable for everyone else (both other pupils as well as the school staff).