Harry, Ron, and Hermione believe that Professor Snape is going to try to steal the Philosopher's/Sorcerer's Stone which is hidden in the castle. They attempt to beat him to it. When Ron is injured, Hermione stays with him and Harry continues on to confront Snape. However, Harry finds Professor Quirrell instead. He is standing in front of the Mirror of Erised, which is apparently holding the stone somewhere. Quirrell explains that it was he who had been trying to steal the stone and that Snape had actually been trying to protect it. A voice from under Quirrell's turban instructs him to use Harry to get the stone. When Harry looks into the Mirror, the stone appears in his pocket. The mysterious voice says to Quirrel, "Let me speak to him." Quirrell removes his turban revealing the face of Voldemort on the back of his head; Voldemort had been using Professor Quirrel to stay alive like a paracite. Under Voldemort's orders, Quirrell attempts to take the stone from Harry, choking him. When Quirrel touches Harry, he dissolves into ashes. Voldemort, now without a body, escapes. In the Hogwarts infirmary, Professor Dumbledore explains that when Harry's mother died to save his life, this act left him with a magical protection which saved him from Quirrel and Voldemort. The Philosopher's/Sorcerer's Stone is destroyed, meaning Nicholas Flamel will die. The heroic acts of Harry, Ron, Hermione, and Neville win Gryffindor the Hogwarts House Cup. Hagrid gives Harry a photo album as he leaves home for the summer, although Harry says he's "not going home; Not really."
Demonhunter
Chosen answer: There are several reasons. First, the position is cursed, so there is little reason to give Snape the job when he will not last any longer than all the previous instructors. If Snape did become the DADA instructor, something could happen to him that could result in his being harmed, having to leave Hogwarts, or be otherwise incapacitated in some way; that would render him useless to Dumbledore as a double agent. Also, Dumbledore trusts Snape, but putting him in an environment where he is teaching about dark magic on a daily basis would be too tempting and emotionally compromising to someone who had been so easily seduced by the dark side. He could possibly relapse. It would be like having a recovering alcoholic work as a bartender. Of course, he does eventually become the DADA instructor, and lasted no longer than his predecessors.
raywest ★
In the movies it is never mentioned that DADA role was cursed by Voldemort.
This is true; though it doesn't say it's not either. With trying to fit 7 long books and years worth of pages of HP information in 2 and a half hours; as long as the movie doesn't say it's not cursed, with our knowledge, there is no problem with reporting that it is. Even directors of non-book movies do this all the time; leave background information out that helps explain things they just didn't have time so they explained it behind the scenes.