A growing literature documents significant differences in college student outcomes between adjunct and full-time instructors, although less is known regarding the causes of these differences. Many existing studies implicitly treat instructor quality—as measured by an instructor’s effect on student outcomes—as a fixed trait. However, instructor quality itself may be sensitive to employment rank, given that adjunct and full-time instructors work under very different conditions. Understanding mechanisms driving these differences is important for informing policy decisions aimed at improving student outcomes. Using panel data on first-semester students at public colleges in Arkansas, this paper first establishes that adjuncts have significantly worse student outcomes than full-time counterparts on a number of metrics. Next, I investigate mechanisms underlying differences in outcomes across instructor rank. I take advantage of the panel structure of the data and use an instructor fixed effects approach to provide evidence that within instructors, student outcomes improve when the instructor is full-time, compared to when the instructor is an adjunct. Results indicates improving student outcomes is about more than just getting better instructors, since instructor quality is not a fixed trait. Rather, factors like an instructor’s conditions of employment and teaching and working environment may affect the outcomes of their students.