I may be wrong on this one, probably haven't paid much attention so correct me if I'm wrong but: sims don't up their skills when they work or go to classes, at least it's an active career, right? Even...
I can't say ive noticed it going to teen from child, thanks for the insight! :) Maybe some of the skills you cant take to childhood and above like movement and potty training that could be why you have to start over at childhood??