The title of this book is The Yearling and the book is actually about … a yearling. Weird, huh? Okay, it's a teeny bit more complicated than that. Flag the fawn is the obvious yearling, but there are plenty of references to Jody as a yearling, too—like Pa's insistence that Jody "ain't a yearlin' no longer" (33), right before Jody agrees to start taking care of the house and farm.
Yeesh. Setting aside that Jody doesn't even have his driver's license yet, what's going on here is that Rawlings is emphasizing the book's main theme: at some point, boys (and deer) have to grow up.