When I was a kid in the 70s, there used to be
something called the "Anti-Coloring Book". I don't
think they make it anymore, but it was fantastic.
Instead of having lines to draw in, it would have a
question at the top of the page and then only the
littlest amount of illustration. For example. One
page might say "They found an alien bird on the moon!
What does it look like?" Then the page would be blank
except for a moon-like horizon line. I think that
book really turned me on to art because it was about
imagination, not color.
Oh- the point is that you could approach a sketchbook
in the same way and adjust it to grade level.