@SimInfinity On the kids I noticed it with, I reset the corresponding skill to 9, maxed it to 10 (again, although the skill bar will stay displayed at 9, you will get the pop message they maxed it out and the traits are still there for hitting it the first time), and then quickly hit at least one skill point for the skills kids can learn in that catagory before hitting save (as someone in a previous said, this is what triggered the glitch). For example, I reset creativity to 9, maxed it out again to 10, then had the child try the piano, pipe organ, and violin before saving. Then I did the same with their mental skill, re-maxed it out, and then tried logic and video gaming. If I remember correctly, the one skill I could seem to get was fishing that used to work, but I'm not sure if it corresponds to a childhood skill.
It worked great for my sims and it did carry over to their teen years. They didn't have any issues learning teen skills and kept the ones they earned from childhood.