The phrase "21st-century skills" is everywhere in education policy discussions these days, from faculty lounges to the highest echelons of the U.S. education system. Broadly speaking, it refers to a push for schools to teach critical-thinking, analytical, and technology skills, in addition to the "soft skills" of creativity, collaboration, and communication that some experts argue will be in high demand as the world increasingly shifts to a global, entrepreneurial, and service-based workplace. This article reports that a group of researchers, historians, and policymakers from across the political spectrum are raising a red flag about the agenda as embodied by the Tucson, Arizona-based Partnership for 21st Century Skills, or P21, the leading advocacy group for 21st-century skills. According to them, unless states that sign on to the movement ensure that all students are also taught a body of explicit, well-sequenced content, a focus on skills will not help students develop higher-order critical-thinking abilities.