Few educational problems have received more attention in recent times than the failure to ensure that elementary and secondary classrooms are all staffed with qualified teachers. Over the past two decades, dozens of studies, commissions, and national reports have warned of a coming crisis resulting from widespread teacher shortages. This article briefly summarizes a recent study I undertook that used national data to examine the sources of school staffing problems and teacher short- ages. This research shows that although these issues are among the most important facing schools, they are also among the least understood. The data also reveal that many currently popular reforms will not solve the staffing problems of schools because they do not address some of their key causes.