For our final elementary school art project this year I chose the artist Man Ray. We learned about his life and work and particularly about his Rayographs. He made these by placing objects directly on photo paper and exposing it to light. Then he developed the paper using darkroom chemicals.
I wanted the students to have a similar experience, but without all the toxins, so I bought Nature Print paper. Its a little pricey so I was only able to get them 5 x 7 inch paper, but I do believe it comes in larger sizes if you have the budget. I asked them to bring in small object that they could arrange on their paper to create an interesting composition. They put the objects on the paper and exposed it to the sun for about two minutes, then submerged the paper in water (in the shade) as a "stop" step. Once they dried they were fully developed.
Here are some of the most interesting ones: