We had an amazing group discussion about staying on topic in a conversation in the first grade class that we are included with. I started by reading the social story I wrote for staying on topic
you can find it here.
I had written up comments that were on topic and off topic for high interest topics in our class. The teacher that I work with loves Hello Kitty and the kiddos love to wear Hello Kitty, too:) Soccer, Star Wars, My Little Pony and Angry Birds were the others I chose. Some other suggestions for the younger grades would be MineCraft, Pete the Cat and Lego Movie.
It will work best if you allow students to go to the topic of their choice. You want them to be excited about it and know some things to generate conversation. I am lucky enough to be in there to support inclusion with my Para Educators so we had enough adults to monitor and shape the conversation. You could do it in small groups, one topic at a time if it is only you.
Although my students have specific needs, this is really helpful with any student and for classroom management as well!