This is #7 in the Roscoe Riley Rules series by Katherine Applegate. It's just the thing for October! First-grader Roscoe is all excited about guessing the weight of the giant pumpkin in the bookstore window to win books for his school library -- and candy for himself. But his superstitious nature takes over when he encounters a black kitten there.
Roscoe's teacher uses this opportunity to discuss estimating, along with superstitions. And she does her best with him, but as he says, "Ms. Diz had that I-need-a-nap look she sometimes gets, but usually not until the ned of the day." Roscoe seems to be sitting in the time-out chair a lot -- he starts the story there, and the rest of the book tells how he got there.
Roscoe reminds me a little of Junie B. Jones because he always seems to be in one scrape or another, but he does not use the kind of baby talk that Junie B. Jones does. These are good beginning chapter books.