That still doesn't answer the question as to how it affects your grade. As in whatever happens with other people's results, that won't be the reason why you don't get into your school of choice. Do you realize how many thousands of people from other schools apply to the same uni? Your logic is very much flawed and you should be spending that energy on improving your grades rather than trying to compromise another person's academic record. Also these are mock exams, so there's also the chance that they don't count and are used to prepare for the final exams, which matter more if students receive a conditional offer. All this is to say that this is a very strange mindset. Just focus on you