It sounds like you come from a very grade-inflated school... I have taken classes at Harvard(an American School FYI) and the University of Toronto, in neither institution does anyone ever look at percentages. Often the mark is developed in relative terms. In both schools, if you everyone got high grades, say 80%+ (yes, that's considered high, because the testsare designed to distinguished the great students from the best students! That's why it's RARE to have students ever scoring above 90[to put things in to perspective for you, even IMO medalists don't score above 80 in math courses and Chem Olympiad winners don't get 90 sometimes]), then everyone will expect an A$SRAPING test coming up. The system is set up so that the FINAL average is a C+ or B-.
Percentage is totally irrelevant!