To succeed in today’s interconnected and complex world, workers need to be able to think systemically, creatively, and critically. Equipping K-16 students with these twenty-first-century competencies requires new thinking not only about what should be taught in school but also about how to develop valid assessments to measure and support these competencies. In Stealth Assessment, Valerie Shute and Matthew Ventura investigate an approach that embeds performance-based assessments in digital games.