Eight years of data from Grand Valley State University Libraries show a positive correlation between in-class library instruction and student reenrollment the following fall semester. Using consistent statistical methods over time, controlling for confounding factors, and using a large population (N>16,000 annually) and strict protocols that restrict library employees from having access to individual student data, researchers have developed a replicable, secure process for exploring the relationship between library engagement and student success that prioritizes data security and subject anonymity alongside scalability. Results have informed modifications to the Libraries' instruction program and have raised interesting additional questions about the impact of having classroom faculty who actively engage their students with the academic library.