This is a two-sided problem. Children may bully and pick on other children and start fights; or they may come out fighting any time they get frustrated, angry, or afraid. Conversely, some children may do things that aggravate others to the point of fighting. Either way, it is a serious problem.
Several things need some thought if you see this sign in your child. Where did your child learn the behavior? Whether he is the aggressor or the victim, he learned the role somewhere. It is not true children often fight. By ten or so, most youngsters never get into physical fights. Those who do usually have a behavior problem. They think fighting is a good way to settle things. They may have learned this from their families or perhaps from living in their neighborhoods or attending their schools. Some places are very rough; and fighting is the normal way to handle conflict. Finally, it may just be one step beyond screaming and yelling, hitting and hurting. If these problems go unchecked, fighting and more serious violence are nearly certain, especially as children get physically bigger and stronger.
If you are at your wits end and your child still fights, say, "Your fighting is a serious problem. I've tried several things over many weeks. (Then list the things you have tried.) You're still fighting. Here's the problem. I want to help you but wonder if I can. However you feel about it, I want you to know where I stand. If you and I can't work this out, it still has to be worked out. The fighting has to stop. We'll start with counseling. If that doesn't help, we'll take the next step. I don't know for sure right now what that is. I sincerely hope we don't have to find out; but I want you to know I will do whatever it takes to help you."
What if your youngster says, "I don't care what you do?" You can say, "That's a shame. I wish you cared. I care and will do what has to be done to help you over this problem. Nothing is happening today so we'll have some chances to talk about this more."