This is not a problem that can be resolved by teachers alone. It requires the team efforts of parents, school boards and community organizations to step in and take action.
It is important to realize that there are myriad factors contributing to bullying and other crimes, including family problems at home, peer pressure, insecurity and more. Some children do have a sadistic streak, and adults should acknowledge this fact. These children are often the ones who end up charged with crimes when they grow up (see my tab Kids in School), but it is possible to guide young individuals and turn them around: counseling and mentors are two of the ways to create change.
Parents of bullies need guidance as well, because family dynamics are a huge factor in a child's mental and social development, as are binary views that everything is black or white. A lack of proper direction at home can lead schoolchildren down the wrong path and the consequences include bullying and crime.
Recently, a reader of my Shield Yourself blog sent me a link to an excellent webpage titled "100+ Statistics on Crime in US Schools" written by Tom Read, a Cybersecurity Researcher. The site contains many ideas., and although the focus is on US schools, the information and advice within applies to other countries too.
I'm adding one of his many helpful graphics here. The image also acts as a link to Tom Read’s webpage. It is comprehensive and well worth the read. It is also worth forwarding the link to others you may be having a conversation with, about some problem child or a traumatized victim or a bully. Just click on the graph to reach the site.