Hi, I'm a math teacher in Florence, Italy, Middle School.
For the first time I've been using Sketchup with 13-year-old students
to introduce and work with solids.
We worked 5 weeks (1 our a week with sketchup) and a the end produced
this video which I find interesting:
Students made all the models with Sketchup,
I made the animation (with Sketchup).
[Unfortunately I will no longer work in that school so I cannot carry
on the work with that class]
I think Sketchup may be used with great results for teaching solids,
volumes, sections and the like.