Sounds like you have a lot of heartfelt advice from your good DIS friends. I probably would not have commented at all if you had not specifically asked, because I am not much of an advice-giver.
This post stuck out most to me. I have a student now who talks nearly non-stop. He is bright, but his constant talking keeps others from focusing, and that is my concern as the teacher of all of them. I do give him extra work and extra jobs very often to let the other kids have a chance to catch up, but as soon as he goes back to the table, he goes right into talking overdrive again. His parents have done the stern talking, threatening, etc., and are supportive of me, but C is just a talker by nature and nothing is going to stop him!
Yesterday, at dismissal, two boys were trying to talk to each other, and C was trying to tell one of those boys something. He kept saying, "D, can I tell you something?" over and over, and D kept ignoring him, as he was talking to another friend. Finally, D said, "C, do you EVER stop talking???" It may take the kids just working things out like that among themselves in a not so pretty way sometimes for him to realize that he has to let others talk, too. It doesn't sound like your situation is that drastic, but this student is just what came to my mind immediately when I read your predicament.
It is great that he has such a wonderful vocabulary, and he is such a fun kid to talk to
when it is time to talk, but during work time, his talking is a problem. I don't want to stifle his enthusiasm for learning, but he also needs to learn some self-control before it affects his ability to have friends without monopolizing conversations.
If Avery can read instead of doing centers sometimes, since that seems to be an issue, that might be best for all. It is a difficult situation for everyone - the teacher who has to be sure all students are getting what they need, the parents who want their children to follow the rules, and the children who are just being who they are.
It shows what a good mom you are that you want to seek advice on the situation and that you are so willing to support both your child and the teacher in this situation.