According to the narrator, how did Laurie change when he started kindergarten in the story "Charles" by Shirley Jackson?

When Shirley Jackson's "Charles" begins, the narrator's son Laurie is "my sweet-voiced nursery-school tot" (Jackson 1).  Even as he turns the corner on his way to school, he begins his transformation to a "swaggering character" (1).  From a sweet and compliant child, he morphs into a noisy and rude character who slams the door, speaks to his father "insolently" (1) and loses his ability to speak proper English, now saying "I didn't learn nothing" (1).

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When Shirley Jackson's "Charles" begins, the narrator's son Laurie is "my sweet-voiced nursery-school tot" (Jackson 1).  Even as he turns the corner on his way to school, he begins his transformation to a "swaggering character" (1).  From a sweet and compliant child, he morphs into a noisy and rude character who slams the door, speaks to his father "insolently" (1) and loses his ability to speak proper English, now saying "I didn't learn nothing" (1).

Laurie begins to come home with stories of Charles, a classmate he says gets in trouble all the time. He has hit the teacher, yells during story time, injures a little girl on the playground, and makes so much noise that he disrupts other classes. After some time passes, Laurie reports Charles has settled down and is rewarded for better behavior. He has a few lapses, and then seems to settle in well. 

After weeks of Laurie reporting on Charles's bad behavior to his parents, his mother, who has missed the parent-teacher conference, attends the PTA meeting, hoping to hear about Charles. This is when she learns from Laurie's teacher that there is no Charles in Laurie's class. She also learns Laurie had a difficult time adjusting to school, but seems to be doing better now. 

Laurie's transformation in school is from sweet toddler to his new alter ego, Charles. Charles is the vehicle by which Laurie reports to his parents his own bad behavior, or at the very least, behavior he wished to engage in while in school. Once he acclimates to school, Laurie reports Charles is behaving better, too. School is truly a transformational process, but it is often a bumpy road!