Charlie Clotfelter is a professor of public policy and economics at Duke. He has studied more things than I can mention here, but two of his most important strands of work focus on teacher quality and school desegregation. Since this is teacher quality week, I'll focus my attention there, but see his book After Brown as well.
Findings on teacher quality:
- Race and experienced teachers: Most of the research on who is taught by inexperienced teachers focuses on how new teachers are more likely to teach in schools with more black kids. Clotfelter and colleagues Sunny Ladd and Jake Vigdor show that even within the same school, black kids are more likely to be taught by inexperienced teachers than white kids. (See publication #3 at the link for more info.)
- Teacher credentials and student achievement: Clotfelter et al., using better data than previously available (a 10 year time frame and data for all teachers in North Carolina), find that a teacher's experience, test scores and regular licensure all have positive effects on student achievement, with larger effects for math than for reading. Of particular interest is their finding that the benefit of experience peaks at 21-27 years of teaching, though like much other research, they find that much of the returns to experience occur in the first few years of teaching.