haven't read any of the messages but here goes.
hmb you are describing my son x2. Not my son now, so much but my son in year 4.
As a parent what helped me was a behaviour book, so, I had easy two way commuication with his teacher, without endless chats after school. If my son was inattentive and silly at school, I always knew. Pattens emerged - we saw if my son was anticipating something exicting, his behavoiur degenerated for days beforehand. The teacher and I set home and school behaviour targets for him - rewards and punishments dependent on his behaviour 24/7. At one point I was giving my son £5.00 for being good for 3 consecutive days and his teacher gave him double bonus points, which worked really well. Then it worked too well and got expensive for me!
Anyway, the teacher was in her twenties, trendy, very passionate about her subject and, according to my son, very strict with high expectations of him. She was on his case all the time. English and music were her best subjects. They are my son's favourite subjects too. For all these reasons he really liked her, respected her and, underneath, wanted to please her. She is still his favourite teacher and he hopes to have her in year 6.
Over year 4 his behaviour and performance improved a lot and he is having a good, peaceful time in year 5 on the whole. The head teacher says he has hugely improved.
Now I asked my son a while ago why he thought he was better behaved now at school. The answer shocked me. He said the single most important reason was to avoid the punishments the teachers gave to naughty children. The punishments he hated the most involved a bit of humiliation - being sent to work with the infants, being made to sit cross legged facting the wall in the the headmasters office. On one occasion, when he was fiddling with his pencil sharpener incessantly, he had to go into each classroom and ask a pupil to show him how to sharpen a pencil. He never really complained about these things to me at the time - in fact he felt they were fair when I talked to him about them. He know he had pushed it and pushed it in the classroom. He accepted the punishments because the teachers were so good, if that makes sense, and he felt valued.
So to sum up, a behaviour book, rewards, good teachers who don't let anything pass unnoticed, plus a small dash of old fashioned humiliation-based punishment seemed to work.
HTH