A rich example of how badge learning can be implemented to support authentic, project-based, student-interest driven learning. This is a program at UC Davis. What pieces of their program could be applicable to a grades 6-12 setting, where badges offer feedback, learning milestones, and open up spaces of possibilities for learning?
Elementary uses badges to signify achievement around character badges. Students demonstrate achievement by submitting two complete projects, researching individuals, creating a puppet skit, etc.