As I have worked with groups of students learning to have purposeful discussions, I've noticed many times it's the same few students doing the talking. Last week as I did a read aloud, the teacher would say, "I keep seeing the same people talking. What do others think?" But no one commented or entered the discussions.
In Martha Heller-Winokur and Marcia Uretsky's book: Fourth Grade Readers, they suggest inviting others into the discussion. By talking to the group about being a strong speaker and listener and sharing the fact that it is important that everyone has a chance to share, hopefully all will soon feel welcome. They need to realize some have difficulty taking part in the discussion. The students all need to be aware of those who have not had a chance to talk and invite them to participate. They could simply call on someone and say: "What are you thinking?"
Give the students a chance to practice this by turning to a partner and say those words. Asking the class for other ways to say it might also help. When students invite others to join the discussion, it shows they care about their ideas. They need to realize this!
Using this strategy as you read a short story to the class, gives them a chance to actually try it out. Prompting individuals to invite others into the discussion may have to be done for awhile! This is not something that happens over night or in one session. It will take many reminders! So, what are YOU thinking?