XP Grading System
Converting traditional letter grades to XP points.
Also see Badges-Awards for additional ideas - using stars and badges for Mastery
Tom Driscoll
Chris Aviles has converted his english class, working with XP points and discussing how he matches XP to letter grades.
http://www.techedupteacher.com/gamify-your-class-level-i-xp-grading-system-2/