Have a look at Ross Greene's book 'The Explosive Child' and his website 'Lives in the Balance'
All behaviour is communication.
He doesnt listen to his teachers or us. He just wants to do what he wants to do
defiance and inability to control his emotions- in particular anger, when he cant do stuff he wants
I'd still ask for this to be investigated by more than a teacher, even SEN teachers get things wrong, he may have an atypical presentation of a condition, they are not qualified to diagnose, nor to say who has nor doesn't have AN based on their observations.
See your GP and ask for a referral, it's a very long very slow process so best to start the ball rolling now. For example it could be caused by slow processing i.e. he doesn't understand what he's being asked, or executive function difficulties, that's when he knows what you want him to do but he can't plan the steps in the task to achieve that.
Also look up PDA strategies and see if any of them help, it's possible he may be demand-avoidant.
OR, none of the above may apply.
No-one apart from a specialist team usually Paed, Ed Psych, SLT and OT can definitely say one way or another, so your best bet is to ask for diagnosis, if he has a specific condition it will be diagnosed and if he hasn't then you'll know.