Let's throw in a driving metaphor, since Jack likes being on the road so much: during his twelfth summer, Jack hits that crucial moment when he's waving good-bye to childhood as he sees it receding through the rearview mirror, but still driving slowly enough away that he can keep it comfortingly in sight. And by the end of the book, he's test-driving the idea of being his own person. While he's certainly not anywhere near grown up by the end (he's really only started), he learns many valuable lessons that prepare him to take on increasingly difficult challenges in the future. Dead End in Norvelt suggests that growing up is a long process—and it's anything but automatic.
Jack's father doesn't contribute in a positive way toward Jack's development. In fact, he mostly hinders Jack's maturation.
Dead End in Norvelt suggests that growing up doesn't necessarily mean conquering your fears, just not letting them control you.