The next day, Hermione and Harry convince Ron to join them on the lawn so they can tell him about Grawp. Ron talks about his saves in the Quidditch match and ruffles his hair, which makes Harry grin—it's exactly what James did. Finally, Hermione tells Ron about Grawp. Ron is incredulous, and insists they have to break their promise to Hagrid. Over the next few days, professors stop assigning homework so the fifth years can study for their O.W.L.s, and several students begin acting strangely. Ernie interrogates people about how many hours per day they study, while Malfoy insists that those students with connections at the Ministry will be favored by the examiners. Neville tells Harry this isn't true: his gran knows the head examiner and she wouldn't do that. Several students also try to buy stimulants, though Hermione confiscates what she can.
Harry's ability to grin when Ron ruffles his hair like James did shows that he's beginning to come to terms with the person his father was as a teenager. Now, he can pick out the parts of his father that he admires or is charmed by, while still recognizing that James was a flawed person who used to be a bully. The strange behavior of people like Ernie reminds the reader that O.W.L.s are extremely stressful for students. Malfoy's insistence that connections lead to higher scores speaks to how he sees adult life working. Indeed, this seems to have worked out for him in the past, considering his extremely privileged life.
Their first O.W.L. is Charms. In the morning, the students file into the Great Hall and take the theoretical exam. They eat lunch and then, in the afternoon, take the practical exam. Harry's examiner seems thrilled to test him. The fifth years go through the same process for Transfiguration, Herbology, and Defense Against the Dark Arts. Harry's examiner for the Defense Against the Dark Arts practical offers him a bonus point for conjuring a Patronus, which makes Umbridge give Harry a nasty look.
The grueling O.W.L. schedule continues to show, by its design, how important these exams are to their futures. Carving out this much time for exams means that students are required to throw themselves entirely into performing well and having things memorized. Harry’s performance in the Defense Against the Dark Arts exam shows how much the D.A. has helped him—and how important a practical education is.
Harry and Ron have Friday off while Hermione takes her Ancient Runes exam. She returns in a horrible temper; she mistranslated one word and someone put another niffler in Umbridge's office. She points out that Umbridge thinks Hagrid is doing it, and Umbridge won't care that Hagrid has an alibi. On Monday, they take their Potions O.W.L., and though Harry finds it difficult, both he and Neville do well in the practical without Snape making them nervous. Harry does his best in his Care of Magical Creatures exam so he can make Hagrid proud, but Divination the next afternoon is a disaster for both Harry and Ron.
When Harry and Neville can perform reasonably well in Potions because Snape isn't there, it speaks to the power of a good teacher to help students succeed—and the power of a poor teacher to keep students from learning the material. Despite the evidence that Snape's behavior is mostly to blame for Harry's poor performance in his class, it's also worth noting that Harry seems to know enough of the material to do well, suggesting that Snape is an effective teacher in other ways.
The practical Astronomy O.W.L. is that evening on the Astronomy Tower. The students set up their telescopes and begin filling in their star charts. As Harry works, he notices several figures, including Umbridge, exiting the front doors. They go to Hagrid's hut and Hagrid lets them in. Harry pretends to concentrate as he hears a roar come from Hagrid's cabin. More loud noises emanate from the cabin and Harry sees the figures trying to Stun Hagrid. The students all watch with horror. Hagrid throws off a few of the people as McGonagall runs toward Hagrid. Four people Stun her at once she collapses, and Hagrid runs away into the forest. Shaken, Harry returns to his exam.
The attack on Hagrid shows that Umbridge is now willing to try to arrest people (hence the accompaniment of what are presumably Aurors) in order to get her way at Hogwarts. This tells Harry that Fudge is moving to tighten his hold on the school even further after losing Dumbledore. By putting Hagrid in Azkaban or restraining him somehow, Fudge would make sure that Hagrid couldn't speak about what's happening at the school with others who could come to his aid. The Ministry (and its microcosm of Umbridge’s regime at Hogwarts) increasingly shows its corruption and willingness to abuse its power.
Harry, Ron, Hermione, and Ernie angrily discuss what happened to Hagrid and McGonagall. In the common room, they learn that Lee Jordan is responsible for the nifflers, and he feels guilty that they were blamed on Hagrid. They don't go to bed until four in the morning. Harry wakes up early so he can study for History of Magic, but it does little good. As he tries to remember the facts of a fight for troll rights, he falls asleep. He dreams he's walking through the Department of Mysteries. The dream seems normal until Harry gets to the room with the orbs—in this dream he sees Sirius. He tells Sirius to remove an orb in the 97th row, and performs the Cruciatus Curse on Sirius when he refuses. Harry wakes screaming.
Harry is seeing things from Voldemort’s perspective in this dream, which allows Harry to feel as though the dream is actually happening in real time. While Harry believes the dream is true at the time, he later discovers it's a trap—Voldemort is manipulating him to try and lure him to come save Sirius. Indeed, many of his most recent dreams have been prepping him for this important play on Voldemort’s part—now he knows how to get to the room with the orbs, which is exactly where Voldemort wants him to be. It's important to note that Harry is more vulnerable to this trap because he's so stressed and exhausted from the O.W.L. the night before, as once again the more mundane concerns of school mingle with the larger forces at work in Harry’s life.