It seems to me that the learning skill is broken. I made an experiment: killed everybody except knight in my party, saved game and killed 10 dragonflies for each combination of learning skill and NPC’s. Knight had 1315 exp before killing dragonflies.
After killing he has:
1555 (+240 exp; 100,0%) with no learing skill, no NPC’s
1575 (+260 exp; 108,3%) with learning skill, no NPC’s
1585 (+270 exp; 112,5%) with no learning skill and a sholar
1585 (+270 exp; 112,5%) with learning skill and a sholar
1595 (+280 exp; 116,7%) with no learning skill and a teacher
1595 (+280 exp; 116,7%) with learning skill and a teacher
1605 (+290 exp; 120,8%) with no learning skill and teacher+sholar
1645 (+330 exp; 137,5%) with learning skill and teacher+sholar

The learning skill promises 9% bonus, so 8,3% is ok, but the sholar promises only 5% bonus, while in fact gives 12,5%. Moreover, combining sholar and learning doesn’t give any additional bonus at all, the same is combining teacher and learning. Teacher, btw, gives 16,7% instead of promised 10%. So, combined teacher+sholar should give 29,2%, but they give only 20,8% (and again, no, it’s not 10%+5%).