Agreed that calling out answerse and fidgeting is completely normal (if irritating to some adults) at this age and especially for a child who KNOWS THE ANSWERS. It's exciting to share knowledge. Child behavior 101. I'm always discouraged when teachers don't understand that this doesn't mean the child has a problem. FWIW, my DS7 had been doing this during the children's program at church. Fortunately, the leader understood that it was because DS does know the answers and so talked w/me and him about instead shaping the responses to appropriate norms (raising hand, allowing others to take some turns, etc.).
You may also want to educate yourself, and then later think of ways to gently educate teachers, about the concept of asynchronous development.
The book "Genius Denied" has some practical tips for working with educators on shaping the learning environment. Available for purchase, of course, or you may be able to get it on library loan.
Your other post noted that you are in a rural area. There may be weekend programs for gifted youth, within a driveable distance, that are affiliated with colleges. That can be a way for your DS to meet others who are "like" him while also learning. At that age, we fed our DS (or rather, he largely chose for himself) a steady diet of books. He tends to delve into one topic, then the next (dinosaurs, ancient civilizations, trains, aliens, etc.). That keeps his mind active outside of school.
