Feelings can be very scary for children, and in the lower grades, they often don't have the vocabulary they need to express their feelings. Frustration, anger, sadness - sometimes even excitement - can all lead to kids acting out in a number of ways.
I wish more adults understood that there is always always a reason for kids to act the way they are acting. They aren't just being "bad" because they want to be - there's something behind it. Some kids hit others when they are angry, some kids put their heads down and become unresponsive when they're sad, and some kids interrupt constantly when they are nervous. There's always a motivation behind the behavior, but children are often not equipped to see this.
One of the things I'm most proud of is creating this silly piece of paper that the kids called the "feelings paper." I did it right before the first day of school one year and I wished I had done it sooner. I've seen similar things with pictures of facial expressions, which I suppose is where I got the idea, but I tried to pick the feelings that would be most applicable for my students.
If you can't see the photo, the paper has a spot for the child's name, and then says "I feel:" They can check "angry," "sad," "disappointed," "worried," "frustrated," "nervous," "excited," "happy," or "I just need attention." They can also write in their own feeling. At the bottom it says "Please tell me why and what would help you.
If I had to pick the single most effective tool I have used in my years of teaching, it would be this paper. I set some ground rules. The papers were in a stack in a certain place and the kids could get up and get one at any time as long as they were quiet. They could also hand it to me or put it on my desk at any time. I would look at it as soon as I could but they understood that I might not be able to do anything immediately. Often, they didn't need me to, because they just needed to acknowledge their feelings.
I'll write later about how I taught some of those words ("frustrated" was a particularly empowering word for many kids). Every one of those words got used, and the most common write-in was "I want to hit someone." (We had talked about how it was OK to feel like hitting someone, as long as you didn't actually hit someone.)
One child whose mom was getting out of jail kept filling out papers with "excited," "happy," and "nervous" all checked. He didn't need me to do anything except read it. One kid, who I wrote about before, checked every single emotion, and filled out a feelings paper probably four times a day. Often he'd write something about hating himself. I don't know if it helped him at all, but maybe it made him a tiny bit aware of the fact that he had a lot going on.