This is the perfect way to have your students PRACTICE painting and mixing colors BEFORE they embark on a final project! :)
I give my students only red, yellow and blue paint (the primary colors) in a palette. They are then tasked with the job of creating the entire color wheel using only the primaries. This lesson includes discovery with paint mixing as well as paint and brush control. My students feel so much more confident with paint once they practice mixing and painting on an assignment that isn't their final piece.
I use this in middle school, but I could see this being great for upper elementary and even early high school (Art 1.)
I cut my 90 lb. drawing paper down to 8.5" x 11" size and put it right into the copy machine where the paper goes and copy this image right onto thick drawing paper. This helps the paint not to make the paper curl up and look sloppy.