I don't know where you got this from, but it's total NONSENSE. A does not stand for "amazing", and the other letters don't stand for the words you've used with them either. The standard alphabetical grading scale is tied to the standard 100-90-80-70-60-50 numerical scale. And on THAT scale, a D is barely a passing grade, and anything below that is considered a failure. An A grade means the numerical score is between 90 and 100. If it's below 90 but still above 80, then the grade becomes a B. And B does NOT stand for "brilliant". It stands for B, and nothing ELSE.