What is the relationship and significance between Charles and Laurie in the Shirley Jackson short story "Charles"?

Laurie has created Charles to serve as his bad-little-boy
alter ego in Shirley Jackson's short story, "Charles." Laurie has apparently been
pampered somewhat by his mother, and she worries before he heads off to kindergarten
that he may pick up some bad habits. Sure enough, they begin appearing at home at an
alarming rate. We can assume that Laurie conjures up the imaginary Charles in order to
explain his own bad behavior without having to admit to his parents that the misbehavior
comes from him. Laurie thus remains the innocent child that his parents see in him while
still admitting to his wrong-doings at school. Critics have explored the possibility
that Laurie is suffering from the early stages of a split personality, and his creation
of Charles lends evidence to this. Surely, his laughing "insanely" at home is a hint by
the author at the problems surrounding Laurie.