This paper uses rich new data on New York State teachers to: determine how much variation in the average attributes of teachers exists across schools, identify schools that have the least-qualified teachers, assess whether the distribution has changed over time, and determine how the distribution of teachers is impacted by attrition and transfer, as well as by the job matches between teachers and schools at the start of careers. Our results show striking differences in the qualifications of teachers across schools. Urban schools, in particular, have lesser-qualified teachers; and New York City stands out among urban areas. Low-income, low-achieving and non-white students, particularly those in urban areas, find themselves in classes with many of the least skilled teachers. Salary variation rarely compensates for the apparent difficulties of teaching in urban settings and, in some cases, contributes to the disparities.

Researchers and policymakers often assume that teacher turnover harms student achievement, but recent evidence calls into question this assumption. Using a unique identification strategy that employs grade-level turnover and two classes of fixed-effects models, this study estimates the effects of teacher turnover on over 600,000 New York City 4th and 5th grade student observations over 5 years. The results indicate that students in grade-levels with higher turnover score lower in both ELA and math and that this effect is particularly strong in schools with more low-performing and black students. Moreover, the results suggest that there is a disruptive effect of turnover beyond changing the composition in teacher quality.

2When given the opportunity, many teachers choose to leave schools serving large concentrations of poor, low-performing and non-white students (Boyd et. al., 2005;Hanushek, Kain, & Rivkin, 2004;Scafidi, Sjoquist, & Stinebrickner, 2005). While a substantial research literature has documented this phenomenon, far less research effort has gone into understanding what features of the working conditions in these schools drive this relatively higher turnover rate (see Loeb, Darling-Hammond and Luczak (2005) for an exception to this). Excessive teacher turnover can be costly and detrimental to instructional cohesion in schools (National Commission on Teaching and America 's Future, 2003). Consequently, many policies, such as mentoring programs and retention bonuses, have aimed to stem teacher attrition, particularly at those schools that experience high teacher turnover. Yet, without a better understanding of the reasons teachers leave, these approaches may not be as effective as they could be at reducing detrimental attrition. This study contributes to our understanding of teacher attrition by modeling the relationship between teacher turnover and school contextual factors -including teachers' influence over school policy, the effectiveness of the school administration, staff relations, student behavior, safety, and facilities.Using a unique dataset that combines longitudinal survey data with district administrative files, we find that school administration plays a particularly important role in teachers' career decisions. In what follows, we briefly review relevant prior research to motivate our study, describe our data and methods, and present the results. The final section discusses the implications of these results, limitations of the study, and directions for future research. Background and Motivation

We developed a zero-to-five index of the strength of accountability in 50 states based on the use of high-stakes testing to sanction and reward schools, and analyzed whether that index is related to student gains on the NAEP mathematics test in 1996–2000. The study also relates the index to changes in student retention in the 9th grade and to changes in high school completion rates over the same period. The results show that students in high-accountability states averaged significantly greater gains on the NAEP 8th-grade math test than students in states with little or no state measures to improve student performance. Furthermore, students in high-accountability states do not have significantly higher retention or lower high school completion rates.

There are fierce debates over the best way to prepare teachers. Some argue that easing entry into teaching is necessary to attract strong candidates, whereas others argue that investing in high quality teacher preparation is the most promising approach. Most agree, however, that we lack a strong research basis for understanding how to prepare teachers. This article is one of the first to estimate the effects of features of teachers' preparation on teachers' value added to student test score performance. Our results indicate variation across preparation programs in the average effectiveness of the teachers they are supplying to New York City schools. In particular, preparation directly linked to practice appears to benefit teachers in their 1st year.