For those interested in K-12 mathematics, here is something that might interest you.
ETS is looking for developers and educators to create a game that acts as a math assessment. We’re looking for innovative ideas that produce evidence of students’ knowledge, skills, and abilities in mathematics. The assessment tasks should be based on a Learning Progression for some field of mathematics in K-12. We are providing two research-based Learning Progressions: (1) Variables and Equality (approximately Grades 5-9) and (2) Linear Functions (approximately Grades 7-10). You are invited to use either of these or supply your own for any other K-12 mathematical content.