Among the journal entries of the late Professor Severus Snape has been found an unusual memoir. It chronicles the occurrences of the day, several years before the coming of Harry Potter to Hogwarts, when a mere muggle not only performed magic, but bested Lord Voldemort himself.
Some might consider this episode a source of deep embarrassment for Hogwarts; the fact that Snape kept the memoir hidden does, some believe, bear this out. As for Snape, however, it's pretty clear that his feelings on the matter were of a less severe nature, and his own sense of mortification the result of something altogether different. A different kind magic, perhaps?