If you have room on your wall, place a string or twine on it and hang your child's art from school on clothespins.
Buy a hanging file for each child, hang it in a central location and label each one with the child's name. Sort through at the end of the week.
Put clear page protectors in a three-ring binder add art to the binder.
There are many of these at thrift stores and you can paint them and add names for your kids.
Have you child pick a few art pieces to mail to family and friends that live far away!
At the end of each week, take a picture of the art to have forever. You can also print out and put in an album!