To dream of a grade or being graded represents feelings about being evaluated or judged on performance. Feelings about the quality of your performance or statements made to others being evaluated.
Example: A man dreamed of his wife grading papers while sitting on his bed. In waking life he was intentionally avoiding intimate relations with his wife and was experiencing anxiety about all his excuses or stories being good enough. He felt that his wife was carefully evaluating how good all his individual excuses were as he slowly ran out of excuses.