The State Higher Education Executive Officers Association's (SHEEO) "Communities of Practice" project builds upon SHEEO's ongoing efforts to measure the capacity and effective use of state postsecondary data systems and provides states with opportunities to develop solutions to common issues with those systems. The sixth Community of Practice convening, "Aligning K-12 and Postsecondary Education," was held December 7-8, 2021, in Denver, Colorado. The two-day meeting included representatives from 13 states: Delaware, Georgia, Hawaii, Idaho, Kentucky, Louisiana, Maryland, Missouri, Pennsylvania, Rhode Island, Tennessee, Utah, and Washington. Teams included representatives from SHEEO agencies, state K-12 agencies, P-20 partnership organizations, state longitudinal data systems, and others. The Community of Practice also addressed the impacts of the COVID-19 pandemic on student transitions and how state data systems can be used to promote equitable outcomes for low-income students and students of color. During the convening, teams explored practical uses of state P-20 data for improving college access, equity, and success and how state postsecondary data can better inform the K-12 to postsecondary pipeline. This white paper highlights key themes and findings of the convening, including challenges and lessons learned from the participating state teams and suggestions of topics for further consideration. Case studies describing ongoing efforts in Georgia and Pennsylvania are included in the appendices. Presentations from the December 2021 convening are available on SHEEO's state postsecondary data website.