When my kids were in elementary school, we had a lot of conversations about bullying. I don't like bullies and I wanted them to know how to handle it when someone tries it (because they inevitably will) and they all knew very early that I wouldn't tolerate them doing it to anyone else.
Their teachers eventually told me that they were the first ones to go over there and stick up for other kids whenever someone was being bullied. I was very proud of them for that.