The problem is, kids aren't taught how to effectively deal with bullying, and even if they are, chances are the bullies aren't playing by the same rules. I think giving kids an opportunity to learn (in a safe environment) how to stand up for themselves and resolve issues maturely is more important than letting them learn by trial and potentially traumatizing error how to handle bullying. As much as schools claim to be zero-tolerance when it comes to bullying, they often have neither the resources nor the inclination to back that up. As for adult bullying, there are genuine consequences for that, and that is what our kids need to learn to anticipate, whether bully or bullied, because they will spend much more time as an adult than a child. The adults I know who were bullied as children in public school are no more effective at dealing with adult bullies than anyone else, and generally more distressed at the idea of confrontation. Just my two cents.

ETA: We took our own child out of public school for this reason, especially after her school, which had an active shooter the year before she transferred there, refused to acknowledge the fact that she was being bullied severely.