My son distracts others in class

So, my son is 10, soon to be 11, and has just finished fourth grade. He is on the autism spectrum but is high functioning. He doesn't suffer much academically, except that he does not stay on task.The problem is that he rushes through his work, finishes early before his peers, and begins to talk to himself, hum, sing, or talk to those seated near him. His classmates find his behavior unacceptable and often get frustrated because (unsurprisingly) they can't focus when my son is making a bunch of noise. It's gotten to the point that anyone seated near him would asked to be moved within a few weeks.He's had this problem since grade 1. They kept calling him "immature" and we kept him back in first grade. Things didn't improve. It's been the same all the way through fourth grade. Average grades but poor marks in classroom behavior, paying attention, respect for others (not respecting their need for a quiet work environment). His teacher for fourth grade really liked him, and was extremely patient with redirecting him to quiet behavior but the need to redirect is almost constant. We've talked to him many many times about needing to focus on his work, remain quiet when he's done, be aware of his body and voice, respect others need for quiet, etc. He doesn't improve. He cries when we try to have the discussion and says he will do better but it's the same thing each year, each report card, each email from his teacher. The school had no real suggestions about how to get him to remain quiet.He's very high functioning. He seems like an average kid except for this issue really. I think that's why it's so frustrating. It seems like he knows better, and is choosing to disregard everyone else in favor of doing what he wants. I've decided thus far to believe that he can't control the behavior, and that is why is isn't improving.I know my parents would have responded with a spanking each time a note or bad report came home but I don't believe that to be a solution. I don't, however, have a better idea. Talking to him about it doesn't change his behavior. He gets upset, cries, and mostly shuts down and just agrees to do better but nothing changes. We tried a using very understanding friendly approach to talking to him about it, a very firm approach to talking about it, we've offered rewards for weeks without issues, we've spoken to the school (they offered next to no advice), and nothing has improved. He just continues to rush through work, make a ton a noise when he's done, and distract his classmates. Anyone that gets seated next to him is unhappy about it and asks to be moved (says his teacher).I want him to be able to stay in his classroom but I know as he moves up into grade 5 and beyond that this behavior will be even more unacceptable and I'm afraid he's going to often be kicked out of class.How do I encourage him to change his behavior or discipline him so he's motivated to remain quiet? Any help is really appreciated! via /r/Parenting http://ift.tt/2tvmBL8