Original: On his eleventh birthday, Harry learns he is a wizard when Rubeus Hagrid arrives to tell him that he is to attend Hogwarts School of Witchcraft and Wizardry.
Simplified: He goes to Hogwarts School of Witchcraft and Wizardry to learn magic. On his eleventh birthday, Harry finds that he is a wizard when Rubeus Hagrid tells him that he is to go Hogwarts School of Witchcraft and Wizardry.