Well, your challenge has already been around for quite a long time, and there are people who completed it using current ruling, so I can see your point, and it makes sense to me (just not because of the TS4 coming and TS3 halting, but still, fair enough).
For the social group cluster,
it seems, the father should work in an University career, which is a rare occurence in the game unless the player puts some effort into it. I think, for this cluster the mother should be level 10 in all social groups (or a popular blogger), get a job in the desired Uni career, wait for coworkers to spawn, woohoo a coworker, 'rinse and repeat'. While it's doable, it is certainly quite challenging. And I can't really compare this to meeting all 5 private school graduates (or 6, to include the public school) -- we can literally bump into those ones on the street without any effort from our side. So, while both tasks are fun, the 'private schools' task would be comparatively so much easier that I don't feel it belongs to the same category as the 'social groups' task.
So yeah, it seems in afterthought that the addition of private schools to the challenge is unneccessary.
Thank you very much for your replies!
P.S. Sorry if this response was possibly not all that clear; English is not my native language.