If you have trouble getting your campers to line up when getting ready to leave an activity, here’s one solution. (This works best with younger kids.) I was taught this during a pre-camp seminar by an “expert” in camp counseling.
What you do is you tell the kids what’s going to happen and what they should do. Tell them that when you say “All eagles to the flock” (the example he gave us), or something similar, they should all line up behind you. You’re going to turn your back to them, count to 10, and give them time to line up. They’ll all come running to line up before you get to 10. When you count to ten. You turn to the right and left, pretending to look for your campers (knowing they’re all lined up behind you). You keep saying that you can’t find them and you’re wondering where they are. They’ll probably start laughing. When they do, turn around fully so you’re facing them. Then act surprised to see them all lined up.
I’ve never tested this method, but it sounds like a good one that might work. I’m going to try this next summer.