California does not have a statewide data system that tracks student progress through K-12 and higher education and into the workforce. As a result, educators and policymakers cannot answer critical questions about student progress, which limits their ability to make evidence-based changes to support better and more equitable opportunities for students. The good news is that the state's education systems already collect the data needed to develop a statewide longitudinal data system (SLDS) and California has several options for creating such a system. These are the key findings of two years of research by the Education Insights Center (EdInsights). [For Part I of this series, see ED574475; for Part II, see ED584700; for Part III, see ED584699; and for Part IV, see ED584698.]