I am the husband of a teacher, just reading though this stuff. Sheetrock is
basically harmless. If you want to use it after you cut it, I suggest putting
a piece of 1 1/2 inch masking tape over the exposed sides. It chips, and
breaks away quite easy, This will eliminate the dust problem as well.
I have another suggestion. Drywall mud is VERy inexpensive. If you made
slabs using it, the kids can carve into it. Not as much dust as drywall, and
cheaper. I suggest making a square box with 1" x 1" wood, filling the box in
with the mud and let dry. then break it into pieces and let them goto work.
And there you have a petroglyph lesson.
(formerly known as Meg's husband Jay)