Great, thanks, yes I've got it to work.
A minor gotcha, I needed to start the separator with a comment -- not quite sure why, as I thought it was being interpreted before Octave saw it. Anyway, it seemed to be needed.
It's pretty neat, actually. The students see two classes that they need to complete/modify for a desired task. Octave sees them as though they are two saved classdef files. Seems to work well!