Painting with watercolor and salt. Wet paper, paint with bright watercolors, then sprinkle with salt and wait to dry. When dry, brush off salt and you have an instant masterpiece. Cut it up for bookmarks or frame.
Celery flower art is another great Mother's Day idea or just a simple art project for the classroom. I think the idea of using food to create art would be an interesting project to bring to the classroom and have students work with and experiment with.