6 year old seems to be contantly arguing with his friends .......

[blushingm]

is this normal. He's always been physical when he gets angry - now he's getting verbal and says mean things and calls other kids name......school think possibly aspergers is this really abnormal behaviour?

Well I don't know about 'normal' I hate that word. BUT I would say from the sounds of it that his behaviour is becoming unacceptable and will start to alienate him from his friends.

I don't know much about aspergers but do you think he could have reasons for his apparent anger and frustration? has he always been like this, in the sense that he is angry?
How does he communicate otherwise?
Is he receptive to help about modifying his behaviour and does he understand that his outbursts are not ok?

why does school think possibly aspergers? the violence and verbal aggression you describe are certainly not diagnostic traits of aspergers IMO

have you tried any managment strategies with him, diversionary tactics, self-control tactics

what does he say when he's calmed down?

(I am not saying that children with autistic spectrum disorders to not show temper or tantrum .. just that it is a symptom rather than a diagnostic)

when he's calmed down he knows it's not nice.....he seems to get on with kids who are older than him much more easily

sounds pretty normal to me