Mrs. Hall stands in front of Ally's desk, encouraging her to finish her page of writing about herself for her new teacher. Ally brushes off Mrs. Hall's insistences that Ally can do it, asking if Mrs. Hall would say the same thing if Ally were going to climb a tree using her teeth. Shay groans that Ally should act normally, Oliver throws himself on his desk laughing, and Albert, a bulky kid wearing a t-shirt that reads "Flint," sits up straight. Ally would rather write about vomiting at a birthday party than about herself.
It's telling that Ally shares that she'd rather write about something objectively uncomfortable and embarrassing rather than write about herself. This suggests that Ally doesn't think very highly of herself. When the other kids laugh at her, it implies that Ally might often get attention for behaving like this.
Mrs. Hall reminds Ally that if she weren't drawing all the time, she could get her work done. Ally slides her drawings of being shot out of a cannon away and explains to the reader that she can't win. She's been to seven schools in seven years and at every one, she does her best—but her teachers say she doesn't try hard enough, is too messy, and is a careless speller. Ally always gets headaches looking at words on pages and often spells words differently on the same page.
Here, all of what Ally says about how she continues to try in school and just can't seem to win suggests that there's more going on than just being a troublemaker. Her drawing, meanwhile, is likely much easier for her, which shows both how Ally uses drawing to escape and that she is good at something.
The rest of the class starts to sigh. Ally knows that they're all thinking that she's a dumb freak and wonders why Mrs. Hall won't let her off the hook like she usually does. Ally tries to stall by asking Mrs. Hall if she's decided what to name her soon-to-be-born baby, but Mrs. Hall won't answer. Ally watches a "mind movie" of Mrs. Hall, dressed as a sheriff, drawing a line in the dirt between herself and Ally, who's dressed as a prisoner. Ally explains that these mind movies happen all the time and they offer her an escape from real life.
When Ally believes her classmates are thinking that she's a dumb freak, it tells the reader that Ally has likely heard this spoken many times—in other words, she no longer needs to hear them say it to know what they're thinking. This sets Ally up as a target of bullying, which likely makes her schoolwork even harder since she knows she'll be teased for her struggles.
Ally picks up her pencil and scribbles all over her desk, and then explains to a flabbergasted Mrs. Hall that the scribbles were there when she sat down. Kids start laughing and Shay whispers loudly that Ally is a freak. Mrs. Hall sends Ally to the office but when Ally pleads to stay, Mrs. Hall seats her at the reading table. While Mrs. Hall cleans the desk, Ally squints at her paper and writes "Why?" over and over again, hoping that someone can answer the question.
Again, Ally's behavior here indicates that what she's being asked to do is likely very difficult for her, and that she's not acting out just to cause trouble. Especially since she mentioned that writing and reading give her headaches, the reader can tell that she's just trying to avoid pain—a perfectly reasonable thing to do.