At two o'clock, when Miss Trunchbull is due to arrive, everyone is ready, and Miss Honey is pleased to see that the jug of water and glass are on the desk where they are meant to be. Miss Trunchbull walks in, formidable and threatening as always, and proceeds to insult the children immediately. She makes them turn over their hands so she can see if they are washed and clean, and picks on one boy, Nigel Hicks, whose hands are filthy.
As punishment, she makes him go stand in the corner on one leg with his face to the wall. While he is there, she tests his spelling skills. Nigel spells "write" correctly on the first try, and tells her that the entire class learned to spell a long word yesterday, "difficulty." Miss Trunchbull does not believe that is true, so she tests a random girl, Prudence, to see if she can spell it. She does, and Nigel shows Miss Trunchbull the method that Miss Honey has taught them to remember the spellings of long words. While still standing on one foot, he sings a simple song, "Mrs. D, Mrs. I, Mrs. FFI, Mrs. C, Mrs. U, Mrs. LTY," to spell the word "difficulty."
Miss Trunchbull thinks it is ridiculous, and tells Miss Honey not to teach poetry while she is teaching spelling. She moves on to test their knowledge of multiplication tables, and a boy named Rupert answers two times seven incorrectly. Miss Trunchbull gets furiously angry, and lifts little Rupert into the air by his hair. She will not let him go until he says that two sevens are fourteen. The children are astounded, and would think she were splendid entertainment if she were not so frightening.
After Miss Trunchbull says she hates small people, she gets angry at a boy named Eric Ink for saying that she, too, must have been small one day. She makes him spell the word "what," and when he spells it wrong she lifts him by his ears out of his seat. She lowers him back when he spells it correctly, and tells Miss Honey that this is the only way to make sure children learn.
She implores Miss Honey to read Nicholas Nickleby by Charles Dickens to learn how headmaster Mr. Wackford Squeers handled the children in his school using physical discipline. Matilda quietly remarks that she has read this book, which Miss Trunchbull does not believe. She asks Matilda's name and when she reveals it, Miss Trunchbull screams that her father is a crook who sold her a faulty car pretending it was new. Matilda diplomatically defends him, saying he is clever at his business, and Miss Trunchbull says she does not like clever people because they are all crooked.
Miss Trunchbull sits down at the teacher's desk and begins to pour herself a glass of water. When the newt that Lavender put in falls out she shrieks and jumps around, then immediately blames Matilda even though the girl insists that she did not do it. Miss Trunchbull continues to shout at her and Matilda gets so angry, and she stares at the glass with the newt in it, feeling some kind of power brewing inside her. She wills the glass to tip over in her mind, and it wobbles, until it finally topples over and the newt spills right onto Miss Trunchbull. Once again she accuses Matilda, but Miss Honey insists that she must have knocked it over on her own since no one went near the desk. She insists that none of the children moved. Furious, Miss Trunchbull stomps out the door.
Matilda hangs back when all the students are dismissed, desperate for Miss Honey to help her understand what she was just able to do. Matilda reveals that it was her who knocked over the glass, even though she did not go near it. She did it with her eyes, by willing it to tip over. Miss Honey at first believes it is in Matilda's imagination, but gives her the benefit of the doubt and asks her to try to do it again. Eventually the glass does fall over, and Miss Honey is astounded. She invites Matilda back to her cottage to have tea and talk about it.
Over the few chapters, the narrator has slowly begun referring to Miss Trunchbull as "the Trunchbull," a nickname the students have given her. This nickname makes her sound more like a beast than a person, blundering around the school like a terrible animal and being cruel to the children. In many ways, Miss Trunchbull is more animal than human; she lacks basic humanity and compassion, and she has little control over her temper. This nickname distances Miss Trunchbull even more from the children she torments.
In the classroom scene, Miss Trunchbull's and Miss Honey's preferred teaching methods are sharply contrasted. Miss Honey prefers to teach through the promise of reward, showering her students with warmth and praise when they master a hard concept. Miss Trunchbull, on the other hand, teaches through punishment, insisting that deterrence is the only successful means by which a teacher can ensure her students learn. It is clear which method Dahl believes is more effective; Miss Honey's students all love her and listen to her, while Miss Trunchbull only succeeds in creating fear.
One of the book's important messages, that it is wrong to loathe people for being clever, makes another appearance in this section. Miss Trunchbull announces that she hates clever people because they are all crooked. While this is true of Mr. Wormwood and his crooked business practices, it is certainly not true of all clever people. This is evidenced by characters like Matilda and Miss Honey, who are clever, but also kind, honest, and compassionate. It is wrong to judge the character of a large group by examining only a select few, but there are unfortunately a lot of people, Miss Trunchbull included, who do exactly this.
Readers have known all along that Matilda is unique, particularly because of her exemplary mind. In Chapter 14, Matilda's uniqueness manifests itself as an astonishing mental power, so unusual that it is practically a miracle. Matilda's ability to influence the physical world around her with only her mind, which is properly termed telekinesis, is a strength that sets her even further apart from the nasty adults in her life. She now has the power to get back at people like Miss Trunchbull for her terrible deeds, taking matters into her own hands.
Chapter 15 is important because for the first time, an adult gives Matilda the chance to explain herself rather than immediately dismissing her ideas and concerns as juvenile or misguided. While Miss Honey does not necessarily believe Matilda at first, she allows her to speak, and gives her the benefit of the doubt. By doing this, she gives Matilda the space to display how extraordinary Matilda truly is, and cements her place as Matilda's only adult ally.