-random distribution of teachers and students among classrooms within schools. We find compelling evidence that teacher credentials affect … distribution of teacher credentials by race and socio-economic status of high school students -- a pattern we also document …

availability of data on all teachers and students in North Carolina over a ten-year period allows us to explore them in more detail … effects of changes in class size or to the socio-economics characteristics of students, as measured, for example, by the … education level of their parents …

to be matched with more advantaged students, and we measure the bias this pattern generates in estimates of the impacts … restrict the analysis to schools that assign students to classrooms in a manner statistically indistinguishable from random … advantaged students, a finding that may help explain why the observed form of teacher-student matching persists in equilibrium …

students from 1999 to 2006, we document and exploit variation by district over time in the math course-taking environment … encountered by students. Within an instrumental variables setup, we examine effects of the policy change on students grouped into … deciles defined by their 8th grade math test scores. First, we find that students took more math courses in high school …