If you dreamed you returned to school, and it doesn’t matter which level of education, the meaning of this dream of being back in school is a message your subconscious has sent. You lack confidence in your present state in life. You have thought of improving yourself. You have the opinion that having better grades will help you. You should reflect on this dream interpretation. If you have someone to talk to and consult, it would be better for you.
If you think that this dream interpretation is inaccurate or does not apply to you, then the alternative meaning is that you were anxious, You thought you had insufficient resources and qualifications, and that you needed to do something to better equip yourself.