Fred and George leave no instructions as to how to get rid of their Portable Swamp, so Filch has to help students across every day. Filch also puts Harry's broomstick in the dungeons. Other students begin to torment Umbridge with Dungbombs, Stinkpellets, and releasing a niffler in Umbridge's office, while others eat sweets from Skiving Snackboxes in her classes and insist they have "Umbridge-itis." Harry also witnesses McGonagall telling Peeves how to unscrew a chandelier. In Charms one day, Ron laments that Mrs. Weasley will think that the twins' departure is his fault, and Harry admits that he gave them his Triwizard winnings. Ron is thrilled, and Harry agrees that he can tell Mrs. Weasley this.
Because the students band together to stand up to Umbridge, they're more difficult for Umbridge to punish. This speaks to the power of working together toward a common goal, and reinforces that there's safety in numbers in situations like this. These students aren't forced to dramatically leave school, like Fred and George were, because there's so many of them misbehaving. A common enemy also helps create a greater sense of unity in the school—students aren’t competing with each other so much now that they’re all fighting Umbridge.
After Charms, Hermione encourages Harry to go talk to Snape about Occlumency, but Harry refuses. He's still having the dreams of the room with the dusty orbs in the Department of Mysteries, and though he insists he tries to empty his mind, he's too curious about the room to try to stop the dreams. Unfortunately for Harry, with O.W.L.s approaching, he often dreams about exams.
Because Harry still doesn't know that the dreams are actually potentially dangerous, he sees no reason to stop them. This again shows how his ignorance means that he comes to trust and rely on something that's actually not trustworthy, simply because it makes him feel like he’s actually learning something in his own way.
Harry and Hermione take their seats for the final Quidditch match of the season, hopeful that without Fred and George around to tease Ron, he'll play better. The Slytherins sing "Weasley is our King" as the match starts and the Slytherins score almost immediately. Hagrid appears behind Harry and asks him and Hermione to come with him, acting secretive. Looking at Hagrid's bloody nose, Harry and Hermione agree. Hagrid distractedly leads Harry and Hermione into the Forbidden Forest with his crossbow. He says that since Firenze left, the centaurs no longer welcome people, since they tried to kill Firenze and Hagrid saved him.
Hagrid walking into the forest armed shows Harry and Hermione that centaurs can be dangerous. The students are taught so little about them (and other non-human cultures) that their ignorance is dangerous, and further can lead to discrimination and prejudice against those they don’t understand.
After a while, Hagrid stops. He tells Harry and Hermione that he's going to be fired any day now, and he needs them to promise to help him. Harry agrees outright, which makes Hagrid tear up, and then Hagrid leads them further. They creep quietly up to a smooth mound of earth, which Hermione and Harry soon realize is actually sleeping giant. Shrilly, Hermione says that the giant's been hurting Hagrid, but Hagrid says he had to bring Grawp back—he's his brother. The other giants were beating Grawp up because he's small, and though Grawp didn't want to come, Hagrid made him. Hermione calls Grawp violent and asks why Hagrid forced him. Harry notices that Grawp is tied up.
The language that Hermione uses suggests that while she's been open to working with giants in the past and integrating them more into Wizarding society, she's actually just as afraid of giants as most other wizards are. Even someone like Hermione, who values diversity and wants non-human beings to have rights and recognition, isn't exempt from fearing beings that are different—even though it's possible that Grawp is only so violent because he doesn't want to be here.
Hagrid says that he needs Harry, Hermione, and Ron to come and talk to Grawp and teach him English. Harry thinks of Firenze's warning that Hagrid's "attempt" isn't working and thinks this is hopeless. Harry wishes he hadn't already agreed to help, as Hagrid grabs a stick and pokes Grawp in the back. Grawp roars and stands up faster than Harry thought possible. He pulls a bird's nest out of a tree and turns it over, and then starts to pull back a tree. Hagrid pokes Grawp again and introduces Harry and "Hermy." Grawp tries to snatch Hermione and then knocks Hagrid over when Hagrid reprimands him. Hagrid leads Harry and Hermione back toward Hogwarts and Harry wonders how Hagrid could ever think it possible to civilize Grawp.
All of Grawp's actions suggest that he's bored being tied up and angry to not be with his own kind—understandable sentiments. In this way, Grawp mirrors the way that Harry felt shut up at the Dursleys' house over the summer. Like Grawp, he was angry and looking for fights all the time, while he was also disinterested in speaking with his captors. This allows Harry to empathize with Grawp and see him as someone worthy of care and sympathy, while also showing that Hagrid's love for his brother is keeping him from making choices in Grawp's best interest.
Hagrid stops suddenly as two centaurs, Magorian and Bane, step out of the trees. They accuse Hagrid of meddling and threaten to hurt him, but Magorian insists that they can't hurt Hagrid since he's accompanied by children. They warn Hagrid to not come back as Hermione pushes Hagrid toward the school. When Hermione suggests that they can't go into the forest with the centaurs behaving this way, Hagrid is dismissive and says that the centaurs won't hurt them. They hear cheering as they reach the edge of the forest and see that the match is over. Harry and Hermione discuss what Hagrid asked them to do, and Hermione angrily suggests that Umbridge is right to want to fire Hagrid for this. She apologizes as they start to hear lines of "Weasley is our King." Harry realizes that this time the words are different: Gryffindor is singing because they won.
Though Hagrid ignores it, Hermione is more than willing to accept the centaurs' ban on humans in the forest. This shows that she recognizes that they're the ones that control the land, and she has no right to trespass and no way of making sure she can do so safely regardless. Harry's insistence that they have to keep their promise to Hagrid shows that he recognizes that loyalty is one of the most important elements in a friendship like theirs. As he consistently does throughout the books, he places loyalty to his close friends above everything else, even his own safety.