You're lucky Hedwig is willing to carry this letter, all the way to Australia. McGonagall is downright furious that you did not tell her, that you would leave right after the Triwizard's Tournament for the holidays with your parents. I told her that, besides training Harry and our end-of-year exams, you simply forgot. I mean I knew after all. Apparently, parents pulling out their children has to be requested in writing. Anyway, maybe your parents can write to her so that everything is in order.