Some people are mad because child sims couldn't paint... but my child sim mastered the social skill and now is advancing in the charisma skill, and can practice speech in the mirror. Is this the same for other skills, ex: when a child sim masters creativity skill they can paint and become a prodigy?

yes when a child masters a child skill they can move onto the adult skill i think

When they master creativity they can learn the piano and violin skills.

Not painting?

I don't think so? May be wrong though. They are still limited to the drawings they have unlocked on their little art tables.
Happy to be proven wrong.

I've never seen the kids being able to paint even with max creativity. The option's not there on the easel.

That's interesting. I know the game isn't that realistic but in the Sims 3 kids could paint like they can in real life.

It's probably an issue with animation, since the easels are made with adult height. You'd think they could pull one of those little step-stools out of their hat, like they did at the sink in previous Sims. (I love the mop that Sims apparently carry around in their pockets all the time - I have to find a mop and bucket, and clean it out, and by that time, the cats have licked up most of whatever I've spilled.)