I encourage discussion in my classroom, and there are times when everybody is talking at once. Instead of scolding kids, focus in on one comment, and in a louder than usual voice say, "Hey! That was awesome! Did everybody hear that?" When I do this, I'm generally leaning toward the student to hear what they say. Then I straighten up and point toward the student when I say "hey" to help get attention back to a single student and stop sidebar conversations.
When everyone is quieted down, call the student by name and have them repeat their comment or observation. Not only does this help you regain classroom control without being negative, it also helps strengthen the self-esteem of students who may be shy. The goal here is to point out that everyone is able to make great, important comments during gospel discussion. It helps you create an atmosphere where students feel their comments are valued and encourages them to comment more when they see that thoughtful responses are treated as special.
Hey, did you hear that? Jake just asked a great question. Repeat that question so we can all hear it, Jake.
I love what you just said. Did everybody hear that? Are you all slamming Jake?
(SLAMMing in my classroom means Sit up, Look at the speaker, Apply the message to your life, Mark your scriptures, Make relevant comments)