Recently, I discovered these shop ticket holders as being available in more sizes than I would have thought. When I found out I could get them to fit 12×18 drawing paper, I knew they would be great for slipping artwork examples inside.
Shop ticket holders are basically a clear plastic sleeve with the opening at one end that makes it easy to slide papers in and out. The plastic is heavyweight and they are stitched together with vinyl trim and feature a reinforced hole for hanging. You can find them that hang horizontal but I only have vertical versions. They are also great to pass around the classroom for closer inspection. Some have an opaque back which makes them only display on one side. I prefer the clear so I can load them with two resources. I have a box of 11×17″ size as well. They are not supremely cheap but I see no reason why they couldn’t last a lifetime. One can buy these from office suppliers and Amazon.