Most of the low-performing schools and students are in urban districts where poverty is high, where large proportions of students have limited English proficiency, and where students perform poorly on achievement tests. Moreover, urban districts face numerous challenges, including attracting teachers to their schools and optimizing their hiring, transfer, and retention policies so that they bring the best available teachers to the classroom setting. What's now needed is an understanding of how schools differ on the qualifications of their teachers and the mechanisms driving these differences. In this article, the authors use the Detroit metropolitan region as a case study in order to (1) determine whether there is teacher sorting across schools and districts, and (2) identify which schools and districts have the least qualified teachers. (Contains 12 tables and 13 notes.)