It doesn't matter if you are teaching kindergarten or high school, there is a good chance that there are bullies at your school.
A lot of times kids don't know how to handle bullies. They are so afraid to stand up for themselves or say anything that they wind up doing nothing. The bullies have their way.
As a teacher you can do a lot to put a stop to bullying. Stand up for kids that you see being bullied even slightly. Call out the bullies that you catch. Embarrass them. Let them know that you aren't going to stand for that kind of behavior. Make a big deal out of the seriousness of bullying.
Your students will be the ones who benefit.