** Not your ordinary endless list - just what's number 1. Just the BEST.
Lining up / Leaving first
Yes indeed, it is as simple as that!
I've tried all the other things and yes, they work but they have their problems. Candy, suckers, chocolate rot teeth and also rot desire. You'll end up having to give more and more and more.... Books, souvenirs - they will kill your pocketbook. Stickers and points become meaningless rather quickly.
Try just giving them a privilege, like leaving the classroom first.
They will love it and it will work.