Peers
In more than half of the incidents where the bullying took place, it usually stops if other students get involved. That means if you see someone being bullied at your school, jump in and support them. Bullies usually pick on easy targets or people they think are alone and can’t defend themselves.
Also, once a bully feels outnumbered or sees that they have to deal with more people, they usually back down. It becomes too much of an issue for them and they don’t want to deal with it. That, and the fact that they may lose social status in the school if they continue.