It's also very hard to avoid - hard to avoid doing both simultaneously, even.

Watching my own nieces, it's struck me that different parts of their minds are maturing at different rates. It's not just that children are any fixed amount less intelligent than adults, and there isn't even a similar vector of factors for different children - children actually acquire capabilities at different points in time, even when they're genetically similar.

So niece A was better at math at twelve than B was at fifteen, vice versa for boating skills, vice versa for impulse control...

It comes down to personality differences, but they're affecting what we'd consider basic cognitive skills in ways you just don't see in adults.