child banging their heads when angry

my 9 year old nephew when he's angry or don't want to do what he's been told to do(like teacher asking him to do his work, or ask him to go to the room when discipline) he hits his head on whatever is infront of him(school desk,bed) how can we help him to stop doing such a thing, to preven damage to himself?

[margypops]

My daughter did this when she was very young and I could only ever conclude it was getting her attention especially when she did it at night on the sides of her crib ..she stopped doing it  once she was older,I never knew why she did it..but it did get her plenty of attention ...

[margypops]

Have you asked him why he does it I am sure it hurts and 9 year old is a bit concerning, how does his teacher deal with it when he does it at school?