This is pretty huge. A lot of my experience growing up in California during the 90s was "tell an adult" and "zero tolerance" coming down from school administrators. This is useful at a very young age, but it neglects to equip the children with agency for when the adults aren't around. You can't tell an adult when you're on the school bus and conflict breaks out. You can't tell an adult when you're out on a soccer trip and people are getting rowdy in the locker room. The bystander effect is very strong in school aged children because we neglect to introduce them to their inherent agency in conflict.
There is also a degree of antifragility that parents could teach as well. Your emotions aren't reality. What people say about you isn't either. Again, these should come from parents.