For students to learn 21st-century skills, we will have to teach them differently than we have in the past. The outdated, transmission model, through which teachers transmit factual knowledge to students via lectures and textbooks, remains the dominant approach to compulsory education in much of the world, yet it is not the most effective way to teach 21st-century skills. Students are not developing 21st-century skills because they are not explicitly taught and because they are more difficult to assess than factual retention. The authors summarize nine lessons from the science of learning telling how students learn 21st-century skills and how pedagogy can address their needs.