behaviour problems

[T5onni]

can someone please help, i have a 9 year old who is getting out of hand, he is constantly lying, fighting with his brother, not doing as he is told, fronting up to me, locking himself in his room, he shakes with anger and has no respect what so ever for me and i am at the end of my tether. On the other hand he is a very very brainy boy. please can someone advise any help. thanks

[Biffalobuff]

Didn't want to read and run, have his school mentioned anything about his behaviour or is it only at home?
It may be a phase, or he may be struggling with something and the behaviour is a sort of symptom of that.
Have there been any big changes recently?