What happened down in the dungeons between you and Professor Quirrell is a complete secret, so, naturally the whole school knows.
J. K. RowlingI knew I could do it all this time,” said Harry, “Because I'd already done it... does that make sense?
J. K. RowlingMalfoy glanced around. Harry knew he was checking for signs of teachers. Then he looked back at Harry and said in a low voice, "You're dead, Potter." Harry raised his eyebrows. "Funny," he said, "you'd think I'd have stopped walking around.
J. K. Rowling