I keep three good How to Draw Manga books in my classroom for lending,
one of which is on Robots and I'm trying to get one on battle scenes. I
had to edit one of them slightly for inappropriate content, but only
slightly.
The books teach very basic drawing content using images the kids already
love, so I figured why not take full advantage of that pre-existing
interest? The figure drawing content is also pretty good, and the kids
know that the facial proportions are not realistic.
I have also used Manga to teach the different things that happen to
faces when they are showing emotions. It has been very useful.
One reason I use a little Manga (depending on the interest level of a
particular class) is to encourage them to draw their own Manga rather
than copying and tracing.