Hi Sharon,
I suggest you make an appointment to see his teacher. Discuss the problems your son is having . Explain how sad he is. Then ask how the school could help him settle. Maybe the teacher could allocate him a "buddy". Maybe you could invite another child from his class around. If the sticker system isn't working, maybe another system might. What reward does he get for his stickers? Is there a reward if he gets 20 stickers etc?
The school has to help him modify his behaviour (as it can't allow rude behaviour to continue) but if the teacher understands how he is feeling, she/he will change her/his attitude towards him. The teacher will understand him more. And maybe the teacher can help the real problem... your son's sadness.

At home just give him lots of love as I'm sure you are. He will settle down. He will make friends.Just make sure he has lots of attention.
What is his behaviour like at home? Was his behaviour good at his old school?

Thanks for your kind reply - I will certainly go and see his teacher and explain the situation - he had a bad start in life up to the age of two and a half - abusive relationship, drug taking father etc. etc. but for the past four years I have turned this around, moved away, got a lovely new partner who loves Max as his own. He was a bit disruptive when he first started his first school but working together with the teachers we got him through it and he was very happy there - he says often that he wants to go back there and wants to be with his old friends.