Many children under the age of 10 display anger because they simply don't know how to express their frustrations any other way - they haven't developed the vocabulary or impulse control yet to do so otherwise. Kicking, screaming, swearing, hitting or throwing things may be the only way they know how to show their feelings.
To help him express his anger or any feelings in general, go to
, print out the feelings chart on that page and post it somewhere where you child can see it.
A couple of times a day (especially when you sense your child is becoming frustrated or angry) ask him or her to show you what face on the chart s/he is feeling. When they point at it, say "oh your feeling _____" so that they begin to learn how to express what they are feeling. If they are able to read have them state the feeling. In either case, ask them whats making them feel that way. If its something uncomfortable have a talk with them about what might help them feel better.
Kids pick things up like sponges and if you do this twice a day with your child s/he will likely be able to spontaneously identify what s/he is feeling within a month. By talking with them about what might make them feel better you are teaching them how to think through their feelings and find ways to soothe themselves. Think about what a difference that could make in your child's life - it will become second nature to him or her and you will have kids that are not only tuned into their feelings, but who also know how to talk about them and how to figure out ways to soothe themselves. And all it takes is a couple minutes a day!!