I think the danger of this statement is in extending "childhood" into adolescence, and then exiting adolescence into adulthood.

We put a relatively arbitrary number of 18 years as the age of adulthood, and treat everyone under that age as effectively a child. However, the transition from child to adult, when we as parents should be guiding them to take on more responsibility and real consequences for foolish actions, should have begun at least by age 10, in my opinion.

They should already BE adults by the time they are legally declared so, not just starting to learn what that means.