Harry Potter and Severus Snape's private lessons

"The curse that failed to kill you seems to have forged some kind of connection between you and the Dark Lord. The evidence suggests that at times, when your mind is most relaxed and vulnerable - when you are asleep, for instance - you are sharing the Dark Lord's thoughts and emotions. The headmaster thinks it inadvisable for this to continue. He wishes me to teach you how to close your mind to the Dark Lord."

- Severus Snape to Harry Potter in January of 1996.

A short-lived series of private lessons took place after Christmas in the 1995–1996 school year, during which Severus Snape attempted to teach Harry Potter the skill of Occlumency. The lessons began under the insistence of Albus Dumbledore, who believed that Harry's mind was vulnerable to an attack by Lord Voldemort, and so the class was designed to give Harry protection from this type of mind invasion.

Overview
Lessons were given once a week, under the guise of Remedial Potions. This was to prevent other people from finding out about Harry and Voldemort's connection in the minds (or as the Ministry put it at that time, Harry seeing things), least by of all Dolores Umbridge, much to Harry's discomfort. Snape made it clear that everybody who seen Harry in Potions class could not deny that he needs remedial help. Harry told his best friends Ron Weasley and Hermione Granger about the lessons, despite Snape forbidding him from telling anyone else the truth.

Dumbledore himself refused to teach Harry for the fear of leaving an opening for Voldemort to attack the headmaster, though Snape took it as the headmaster has the right to delegate less-enjoyable tasks to other teachers. Sirius Black was rather displeased with Snape being the teacher, while Remus Lupin was confident due to Snape's mastery in Occlumency.

Under Snape's tutelage, Harry repeatedly had his mind attacked in order to train him. Snape also ordered Harry to empty his mind every night as practice. Unfortunately, due to the mutual animosity between the teacher and student, Snape was unkind and discouraging in his methods despite his own mastery of the skill, while Harry did not take Snape's lessons too seriously, and neglected to practice. Coupled with Harry being emotionally open at all times, the lessons did not progress much, with only rare instances was Harry able to resist, if only briefly.

Unenthusiastic though both were, Snape was nonetheless disappointed with Harry's lack of progress and efforts, as Snape himself had to give up his evenings for these trainings, and would scold Harry viciously for negligence.

Cancellation
"Get out, get out, I don't want to see you in this office ever again!"

- Snape cancelling the lessons.

The lessons were ultimately cancelled when Harry saw a memory in the Pensieve of his father hanging Snape in the air by his ankles and was caught by the Potions master, while Snape postponed the lessons in order to rescue Graham Montague from being stuck inside a toilet. Snape was so furious at Harry that he threw the boy out of his office and forbade him from ever returning. Despite Sirius Black and Remus Lupin's insistence for Harry to continue, it was never followed through. Harry was ultimately left open for Voldemort's deceptions.

Impact
As Harry was an emotional wizard, he was never able to master Occlumency as a skill; even Dumbledore had to admit that the lessons were a "fiasco". However, he was eventually able to gain a degree of control over the unique connection he shared with Voldemort by focusing on feelings of grief or love, such as those inspired by the deaths of Sirius Black or Dobby.

Behind the scenes

 * In LEGO Harry Potter: Years 5-7, Snape teaches Harry a different spell other than Occlumency in these lessons. In the console and PC versions, it is Focus, while in the handheld versions, it is the Imperius Curse. Regardless, he still appears to be using Legilimency to penetrate Harry's mind during these lessons.

Appearances

 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows: Part 2 
 * LEGO Harry Potter: Years 5-7