For me the only adult skill my child was able to learn was the violin skill. She is simply unable to learn any of the other adult skills. charisma, video games, mischief and logic. Just to name the ones I've tried up until now. Pretty sure the rest is going to end the same way. Also remember a child was able to learn the "acting skill" in the past, but that might not be the case anymore. Can't be sure, had a rather long break from the game, so that might not be a bug.
As a previous commenter also said, I've also tried the cheat code to get the skill to level 1, but it doesn't work. Same goes for level 10 actually.
Tried to contact support, but the only thing I was told to do was reinstall origins because of a "sync error". And after that they sent me a message on my e-mail with instructions on how to possible get it to work after reinstalling origins. I would happily share the mail I got, if it worked. But seeing as it didn't work at all,I'm not going to. Unless people wants to try it out themselves.
Oh and I might mention, that like others, I've only gotten it to work on new save games, which frankly is annoying.