Refer to the "What Did I Score" button for all XP to grade conversions. In order to complete the challenge and have a shot at a perfect score, you need to complete Periods 1, 2, and 3. For bonus points, complete OT.
    Once you have made it through each period of the game, be sure to request your work checked to get access to the Under Review password that will unlock all video solutions. 
    Good luck!