Volume 3, Scaling & Perspective, begins to tackle a subject that mystifies many, including many professional artists. The book walks the students up through scaling, laying out landscape and then to architectural drawing and vehicles. It has inbetween lessons in techniques of drawing circles in perspective, toning landscapes with ink and a lesson in optics - how we see the world around us and how the artist translates, via geometry, the 3 dimensional world into the 2 dimensional world of drawings.
This book, because of its subject, is at the upper end of what a 1st through 3rd grade student can expect to do. This is not that 'they can't do it', it is just the concepts start to get advanced beyond their understanding as they are learning in school. The book is recommended for home schooling, but should be reserved for 4th graders and above. Again, 4th graders through High School will have no problem with it and will be impressed with the level of art they start doing as a result of using this book. Watt teaches this material to 1st and 3rd graders in his classes but ensures them that 'they don't have to understand everything' and just to use 'what they understand'. This works out well for them.