This is a good question and can be handled similarly with younger and older students. I tend to raise my hand and wait until the room is quiet. It takes some time but is effective. Then I reiterate expectations that when my hand is raised, the room should finish conversations and quiet. With adults I will make eye contact and ask them if they have any questions I can answer. I rarely have consistent overtalking. Also if its content area students are talking about, its an opportunity to discuss more what the conversation is about.
