Found silveroak's take on this, it's not how I presented it, I'm afraid:
"Any season you take a class in Latin you can split your experience between the class topic, Latin, and teaching, but the class topic must be at least 50% of the points.
If you are taking a class of Latin (where Latin is the subject being taught) then the points may be split between Latin, Artes Liberales, and teaching, but again Latin must be the majority of the points. In both cases the majority value is calculated before any affinities, but after apt pupil."