To succeed in college, career and life in the 21st century, students must be supported in mastering both content and skills. This Implementation Guide presents state leaders, policymakers and/or district and school leaders with assessment tactics and examples to assist in statewide 21st century skills initiatives. The Partnership for 21st Century Skills has issued five brief, user-friendly guides, one for each of the P21 support systems: (1) Standards; (2) Assessment; (3) Professional Development; (4) Curriculum & Instruction; and (5) Learning Environments. It is worth noting that these support systems are not merely ends, but means to a greater goal--to help children develop the cognitive, academic, emotional and physical competencies they need to succeed in 21st century life. The Partnership recognizes that taking an aligned, comprehensive approach across all five support systems is a significant challenge for all educators. The Implementation Guides have been developed to help support this difficult work. While not every recommendation and example will apply to every state, the hope is that the resources will help jumpstart efforts to produce more capable, successful 21st century students and citizens. (Contains 5 resources.)