Seventh grade students had to fill all of the black paper with oil pastel. They also had to show movement of the water with line, have at least three lily pads (one completely on the paper and another going off the edge), at least one flower and at least one complimentary color pair. We were running out of blue by the end of the project but many students layered colors to make the water look even more interesting. Check out my rubric here, which you are free to use. (We use North Carolina State Standards, but feel free to make changes to it to suit your needs.)
Check out my Pinterest page, for more seventh grade art project ideas.