A few days later, Parvati curls her lashes at the breakfast table in preparation for their first Divination lesson with Firenze. Hermione darkly says that Umbridge is going to get even nastier after Firenze's hiring, since she hates part-humans. Ron and Harry follow Parvati and Lavender to a classroom off of the great hall, which looks like a piece of the forest. As Firenze greets Harry, Harry notices a hoof-shaped bruise on the centaur's chest. Firenze greets the class and notes that he's no longer welcome in the Forbidden Forest. Dean asks if Hagrid breeds centaurs, but Firenze quietly and seriously says that centaurs aren't "playthings of humans." He explains that his herd banished him because they see working for Dumbledore as a betrayal.
Dean's question, while asked in earnest, is nonetheless extremely offensive to Firenze. The fact that Dean didn't ask it to be mean reminds the reader that Dean hasn't grown up in the Wizarding world, knowing that centaurs are their own people with their own culture—he knows next to nothing about them. It’s telling, then, that even a child like Dean has the ability and the willingness to learn to treat Firenze and centaurs with respect and kindness—unlike Umbridge, who should certainly know better.
Firenze asks the students to lie down and dims the light. Stars appear on the ceiling, and Parvati starts to point out how the arrangement of the planets causes burns and accidents. Firenze says this is nonsense. He says that centaur wisdom looks for events on a larger scale and mentions that centaurs have been tracking a coming war for a decade. He has the class burn sage to look for clues, but nobody sees anything. Harry is perplexed that Firenze's whole point seems to be that no knowledge is foolproof. When the bell rings, Firenze asks Harry to stay behind and tells him to pass on to Hagrid that his "attempt" isn't working. When Harry passes on Firenze's message, Hagrid seems offended.
Firenze offers a very different kind of wisdom than the human teachers at Hogwarts, but it is no less valuable. The fact that Firenze's lesson centers on the idea that no knowledge is foolproof suggests that in order to move through the world successfully, Harry should endeavor to acquire knowledge everywhere and every chance he gets—for only through looking at things holistically and from a variety of points of views will Harry be able to come to reasonable conclusions about the world.
The fifth years begin suffering from O.W.L. stress and the only thing that makes Harry happy are D.A. meetings. He introduces Patronuses one night and several students, including Seamus, experience success conjuring them. Suddenly Dobby enters the room, looking terrified. Harry ascertains that Umbridge found about the D.A. and sends everyone running. Harry races for a bathroom, but Malfoy hits him with a Trip Jinx. Umbridge comes around the corner, looking delighted. She walks Harry to Dumbledore's office.
Notice that it's Malfoy who catches Harry, not Umbridge. This shows that Umbridge is weaponizing the divisions already within the school so that she can gain control over the students she doesn't like. In doing so, she creates another hierarchy of students and exacerbates the issues the Sorting Hat mentioned in its song.
Dumbledore's office is filled with people, including Fudge, McGonagall, Kingsley, and Percy. Fudge asks Harry if he knows why he's here. Harry catches Dumbledore's eye, sees him shake his head, and says he doesn't. Umbridge leaves and returns with Marietta, who hides her face in her hands. When she moves her hands, Harry sees "SNEAK" written in purple boils across her face. Fudge jumps in surprise and Marietta wails and covers her face again. She refuses to speak, so Umbridge says that Marietta told her about the D.A.
Umbridge's inability to empathize with Marietta and understand how embarrassing it must be to have "SNEAK" written in boils on her face shows again that Umbridge only wants her relationships with the students to flow one way: she wants them to serve her, and has little interest in taking their concerns, valid or otherwise, seriously.
Umbridge reminds the room that in the fall, Willy Widdershins reported to her that he heard Harry in the Hog's Head, setting up an illegal society. Dumbledore interrupts and points out that at the time, the society wasn't illegal. He asks for proof if the meetings have continued since then. Harry then hears Kingsley whisper and feels something brush against him. When Umbridge asks Marietta to tell them about the D.A. meetings, Marietta, whose eyes are strangely blank, says there haven't been any. Umbridge loses her temper and shakes Marietta, but Dumbledore draws his wand and Umbridge lets go as though she was burned. Umbridge composes herself and pulls out the member list of the D.A.
Again, Umbridge's choice to shake and yell at Marietta shows that she doesn't actually care for students at all; she only cares about bringing the school under Ministry control, and is willing to use and abuse students when it suits her. Dumbledore, on the other hand, shows that he cares deeply and impartially for his students when he stops Umbridge from shaking Marietta. It’s suggested that Kingsley discreetly wipes Marietta’s memory here.
Fudge accepts the list and is shocked to see that the group is called Dumbledore's Army. Dumbledore says that he recruited the students himself and tonight was the first meeting. Fudge is furious, and Harry tries to stop Dumbledore when he realizes what Dumbledore is doing. Dumbledore remains calm as Fudge prepares to escort Dumbledore to Azkaban. With a smile, Dumbledore says he has no intention of going to Azkaban. When Fudge tells Kingsley to take Dumbledore, there are a few bangs, McGonagall yanks Harry to the ground, and he looks up to see everyone except Dumbledore unconscious. Harry tries to thank or apologize to Dumbledore, but Dumbledore tells Harry to practice Occlumency and touches Harry's arm. Harry again angrily wants to bite him as Dumbledore grabs Fawkes and disappears. Everyone else comes to and races after Dumbledore.
Dumbledore and Kingsley work together to put all the blame on Dumbledore and keep the students out of harm’s way. Though Dumbledore's parting words to practice Occlumency should give Harry important information about what's going on and his role in it, the fact that once again, this is a quick meeting in which Dumbledore won't tell Harry anything that Harry wants to know keeps Harry from taking Dumbledore’s request seriously. Dumbledore again refuses to include Harry in any of his planning or interpretations of what's going on in the world, so now, Harry feels even more alone with his departure.