"My guess is that the rationale is that this isn't a copyright case, but a licensing case. Thus the education group, AFPA, can actually be a party to the lawsuit. Still, it does raise questions over who has the right to make sure the GPL is enforced."
Yes this is not a pure copyright case since the copyright owner isn't involved at all.
About the question, it has been answered clearly: any person who is provided a GPL software binary can ask its provider to give him the corresponding source. Note that neither Edu4 nor the judge raised any doubt about that, and the only valid basis for the source code request is in the GPL, ie it's not in a separate contract between Edu4 and AFPA.
So at least in France this is now quite well settled.