Use a conch (or similar.
Remember Lord of the Flies?
That's the behaviour management strategy used to control a large group discussion.
Have a discussion time where only the CONCH holder can talk.
This activity is best completed in a circle but can be achieved while students are seated. Instead of a conch, use a very soft foam ball that can be passed by throwing without taking out an eye.
You can let out a little aggression here. When it's your turn with the conch, lob a fast ball at one of your little turkeys who might not be watching.