I did badly in exams this time round and I feel really down?

I have always scored straight As, yes, straight As for my high school mid-year examinations. However, this time round, I did quite badly and failed quite a number of subjects. It's not that I did not study but I just scored very low this time round for no apparent reason. Even my most dependable English abandoned me this time round too. I feel really dejected and I really worry about how my parents will feel? Any tips?