After running over I-Lost-Count (I'm guessing more then 20) reruns of the first two terms I think I can make a conclusion:
Every single run except for the last one, I used the weekend in to grind the 3 major related skills to max, and in the second term I would fail 1 or 2 classes consistently. Not only the paper one, also one of the exam ones would be lower then A+, despite doing the same amount of activities as far as homework and classes are concerned.
In the last one I purposely avoided any skill building outside of class, and ended the first term with all 3 skills at level 6. Then in the second term I would avoid building skill outside of class even more to leave something to work with for the third term. And lo and behold, she got an A+ on all 4 subjects WITHOUT any studying.
I also noticed grading doesn't appear to be linear to job performance, as in both terms of this last try I got an A+ with anything from 78% to 88% while in the maxed skill saves I would get a lower grade on a 98% to 100% job performance. What these other factors are I can't tell from the Show Sims Info mod I used to keep track of this progress.
This does give a problem for any semi-related second or later degrees, as by then your sims will have very high skill levels in the overlapping skills, and therefore risk failing despite putting in all the work. Which is a bummer for my new ultimate sim challenge as I want to have her work and get all 13....
As a WORKAROUND I suggest that at the start of any term you check if your sims has maxed out any of the two skills that are in that terms classes, and use either cheats or mods to lower that skill to 9 or perhaps even 8, to make sure that there is skill building available that term.
I hope that this data helps the Devs locate the bug which turns out to not only affect the paper class but also other classes (although not as much) and fix it in one of the future patches!
