Scratchboard is thick paper that has a layer of black ink printed on top.
The artist uses a metal tipped tool to scratch away the black ink leaving the white to show.
It's drawing in reverse. It's tougher though. It takes skill to get it to scrape the way you want.
Each of the 5th and 6th grade class started by drawing with pencil lightly an ear of corn. Then after finishing the scratching they added color with sharpies.