The Watson children attend Clark Elementary School, and Byron shortens the name of the school to "Clark" when speaking of it. Poindexter is a name which is associated with a stereotypical "nerdy" person, someone who is highly intelligent, and considered very "uncool" because of this. Kenny is an avid reader whose precociousness has been recognized by a number of the teachers at the school. These teachers draw attention to his intellectual abilities, having him read to the older children, and using him as an example to shame his older brother Byron, who does not share his reputation as a model student. Unfortunately, the extra attention given to Kenny because of his academic prowess does not endear him to the other students, and he is the object of much teasing because of it. Kenny is called a variety of unkind nicknames referring to his nerdiness, including "Poindexter," "Professor," and "Egghead."
When the schoolbus arrives to pick up the children every morning, Byron and his trouble-making friend Buphead sometimes do not get on it, slipping away and ditching school. When Byron makes his escape, he usually says to Kenny as he walks by, "Give my regards to Clark, Poindexter." As explained above, "Poindexter" is his derogatory name for Kenny, and "Clark" is the name of the school; Byron is telling Kenny arrogantly to in effect say "hello" to the school for him that day, because he will not be there to do it himself (Chapter 2).