One of the kids in my Village is 9 and in the skill coloumn it says "Ma…

Sometimes, children are born with some inherited skills, also it is possible with an Island event that they could master a skill before they are old enough to build it. I once had such an event where the birds taught my children about "Parenting and one about 12 at the time had his bar entirely full in the parenting. if I tried to breed him. it said. "this villager is too young."

Also, sometimes they might find something during an event and they change bodies with someone else. I think in the secret city you get some sort of achiement called child prodigy when they are masters before 14 or mabye it's 18.