To help teach organizational skills and to keep track of unfinished class work, I use a file crate. Each child has a folder with his/her name and a number. If we run out of time to work on a project or paper, it goes in the folder until we have free time again. This also keeps papers from getting wrinkled and torn in the desks, or taken home by mistake.
If you use a number system to sort and grade papers, you can also have each student write his/her number on the paper along with his/her name.