Change the layout of your classroom on a Tuesday evening.
Seriously. They have no idea what to do when they walk into a newly arranged room. I have had several kids for two years in a row and they sit in the same seat every day for both of those years. Every student who has walked through my door has stopped dead in their tracks and said, "Whoa*."
When I moved into this room, I had three rows of desks with just enough room to walk around the ends. If someone on the other side of the room raised there hand, I just waved. I had no good way to get there. Now I have an outside "U" with two mini-rows (kids call them islands) in the middle. And I love it. I can get from point to point in the room without any major student rearrangement.
It could be that they are still stunned, but I have noticed a change in the kids as well. They seem more attentive and less likely to strike up a conversation with their neighbor. Maybe they feel less isolated.
Even better, we have renamed this room. My principal has always called it the "chemistry lecture room.**" One of my kids has christened it the "chemistry discussion room."
*This is a direct quote.
**I have given up trying to convince him that I rarely lecture.