Laurie essentially is an undisciplined, disrespectful, deceitful, conniving, but clever and very intelligent child.
From the exposition of the story, it becomes apparent that Laurie is undisciplined and willful as he "renounced" his baby overalls and is now a "swaggered character" who no longer waves good-bye to his mother. When he returns home the first day he slam[s] the door open and shouts with a "raucous" voice, "Isn't anybody here?"
Yet, the parents are surprised to learn of a boy named Charles who is purportedly "fresh" when he speaks to his teacher, and then even strikes her. (Laurie smiles as he relates this.) One day when Laurie recounts that Charles has let the seesaw hit the head of a little girl, the mother naively asks her husband, "Do you think kindergarten is too unsettling for Laurie?" In another instance of irony, Laurie returns from school late, "yelling" all the way as he comes up the hill toward his mother that
"Charles yelled so in school they sent a boy from another class to tell the teacher to make him be quiet, and so Charles had to stay after school."
Laurie finally becomes so willful at home that his mother states,
Laurie did a Charles when he filled his wagon full of mud and pulled it through the kitchen....
And, yet, Laurie's parents are still deceived about their child. Even after he tells them that Charles prompted a girl to say an offensive word in school, and then says the same word at home himself some days later, the parents do not make the connection. Indeed, there is no question that Laurie is far more clever and creative than his gullible parents who must be told by Laurie's teacher that there is no Charles.