Regarding the late assignment of drafting-shapes-on-3D-printer-software that has to be performed on special computer/software to which he has limited access: note that BlocksCAD and Tinkercad are both student-oriented, 3D design software that run in a browser (no need to install any software) over the Internet, capable of producing STL files suitable for 3D printing. Tinkercad has a visual, drag-shapes-around-and-click sort of interface; BlocksCAD takes a more programming language approach (it's essentially the visual Scratch programming language combined with the OpenSCAD design package -- if your son has done any computer programming previously, this may be appealing). Autodesk, maker of a variety of professional quality CAD packages, makes some of its CAD software available for free to students: for instance, one such higher level package is Autodesk Fusion 360. And there are other free-version packages for 3D design, producing output suitable for 3D printing, also.
So depending upon what the assignment really involves, a question that would occur to me would be whether it *really* needs to be done on that limited-access platform: could the assignment be modified for your son so that he could work on it (or something equivalent to it) on a more easily accessible platform? Also, some people (including me) have quite strong preferences regarding the operation of user interfaces for designing: maybe your son already loves the software the class is using, but if not, he might find some other software interface more to his taste. Or even if he really and truly has to complete the assignment on the school computer/package -- maybe some more leisurely, on his own time, experimentation using a different (but free! and accessible!) design package would enable him to feel more capable and be more efficient during his limited time on the school computer/package.
