Ha! I did the same thing for History and English in NZ. We had 2 mock exams during the year leading up to the main one and I used all the same essays in all of them. My teachers weren't too pleased about it after the 2nd mock exam (and my English teacher actually failed me for it - though that didn't count) but I got a good final grade. Ironically my father is was teaching secondary school English and History at the time.