Shading Assignment Suggestions
The assignment suggestions are not listed by age or difficultly level but, of course, the instructor or the person completing the assignments can decide to what degree any assignment should be done.
John Ruskin's Book
The Elements of Drawing: in three letters to beginners.
Shown here- a photograph of my hard copy of John Ruskin's Book (purchased from Amazon)
If you decide to use "The Elements of Drawing: in three letters to beginners.", you may (if the pdf is still available) download a pdf version from books.google or do as I did and purchase a hard copy.
At the online store Amazon there are two versions of the book:
The one I have: digital images of the 1876 copy (is just like the google copy)
A facsimile reprint of the 1895 copy
I do not know what the difference is between the two copies.