A grade is read as judgement on your effort and how you rate yourself. A poor mark points to fear of falling short; a high one to the wish for recognition.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.