There is a skill gap between today’s high school graduates and the needs of employers related to the demands of the 21st century. These skills, frequently referred to as 21st century skills, include students’ ability to problem solve, communicate, be creative and innovative and work in teams. This multi-site case study explores how leaders in four public school districts in the EdLeader Network utilize curriculum and assessment systems in support of developing 21st century skills in students. Key findings of the study include the importance of establishing a common definition and understanding of 21st century skills early in district work, utilizing a group of “early adopters” or “innovators” to help build capacity in administrators and staff, and working to integrate 21st century skills into existing curriculum and assessment structures. Process findings highlight the interconnectedness of capacity building, systems work, and translation and implementation of 21st century skill knowledge by district administrators and staff. Results suggested integrating 21st century skills into curriculum systems is a precursor to systematically assessing and reporting on the skills. A limitation to the study was the focus of EdLeader Network districts, thus the results are not generalizable. Further research is needed to more deeply understand the processes, resources and tools utilized by districts doing this work, without the support inherent in the EdLeader Network.