First, someone who bully others, having something wrong during his/her lifetime. This action may attribute to parent's education, culture, or school. But the people who suffered from a bully needs their right back.
Second, maybe making a prosecution is too extreme, however, if the victims couldn't do anything, the bully wouldn't stop.
Therefore, we can not only make use of education to decrease the rate of bullying but also ask the bully for what they have done.
Teachers have a responsibility to protect their students. If they took that responsibility seriously ans stayed aware, the bullying would never have gotten to the point of prosecution. Prosecute the school, not the bully. The bully is a child who cant make good decisions, and jail or fines will not internalize anti bullying messages.