My info might be irrelevant... Well, it's been quite awhile since I taught. On a few occasions, students were talking during my lecture in a large hall while I was speaking and writing on a chalkboard.
I slowly turned, stared at them, and said "You have all of the time in the world to talk BEFORE and AFTER class, surely you can wait 50 minutes to talk some more." They shrugged down and were silent the rest of class. Of course, I am tall, foreboding, and I give a face that scares myself at times.....I guess I don't have good advice!
