"Student Demographics, Teacher Sorting, and Teacher Quality: Evidence from the End of School Desegregation,"

http://www.eurekalert.org/pub_releases/2009-05/uocp-stc052109.php

This paper will be published in the upcoming volume of the Journal of Labor Economics and is written by C. Kirabo Jackson.

The paper uses the end of a policy - a busing program that distributed the minority students across schools in the area, to investigate whether the proportion of minority students in a school has a causal relationship to teacher quality, as measured by years of experience, certification test scores and ability to improve student test scores. They found that the schools that had a large increase in the proportion of black students after the policy was discontinued had a decrease in the number of high-quality teachers.

I will update this post with the link to the article from the Journal of Labor Economics when it is available.