Update: This model now has a smoother deck and wheels with a bit more flair.
This is an easy, fun and satisfying project to design and print that's well suited for students new to 3D modeling. Following along with this Inventor Studios Tinkercad tutorial when designing the board and this one when designing the wheels. Follow the entire collection to develop and refine your modeling skills.
"Japanese Erasers" have been very popular with kids for several years, as have keychains that hang in bunches on the outside of backpacks. I find both, though the erasers in particular, to be excellent 3D learning tools. When taken apart they're reduced to basic 3D shapes that can be modeled on the computer then reconstructed as 3D printed objects, which are wonderful keepsakes of their class.
I consider joinery to be an important early skill for young inventors to develop. So the most interesting designs in my class are those that consist of multiple pieces that are interesting whether together or as a pile of printed parts.
The creation of this simple object, together with others that I've uploaded to Thingiverse, are useful exercises for anybody learning 3D modeling.
I printed in ABS on a Makerbot clone with an extruder temperature of 220 degrees, HBP at 100 degrees, and 0.2 resolution.
I use about 35 mm of filament for the axel. Once the wheels and deck are threaded I melt the ends using the hot-end of the extruder to create filament blobs so that the wheels stay on.