When I teach my summer classes, I always have the kids make sketch books.
That way, as soon as they get there, they pull out their sketchbooks for a
little free draw or ideas for their work.
I have found it to be a great transition and soon they are all quietly
working and they have the "free-draws" out of their system.
I also take 15 minute breaks and lunch breaks with sidewalk chalk. That is
very successful!