Kids can also have a horrible time of cleaning up the mess they make before the final bell goes.
A way to help with the tidying of the messy classroom is to play a little "game" I like to call "Mystery Mess"
Here is how it works:
Bring something to give away to the students (stickers, pencils, erasers, little notebooks - just go to the local Dollar Store and see what you can get)
Some prizes I've acquired over the years...
Continue telling the students that whoever cleans up the mystery mess is going to get a prize.
They will (hopefully) all start cleaning because they want that prize.
Watch the mess that you picked (if the room is really messy you can even pick 2) to make sure you see who ends up tidying it up.
Once the room is clean tell them what the messes were and who you saw cleaning them (and give them their prizes)
Now the room is tidy and you can leave pretty well with the kids at the sound of the bell because you don't have to do the cleaning yourself!*
*only you wouldn't dare leave at the bell because I already taught you not to do this in "Don't Leave Too Early"