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In recent years education reformers have focused a great deal of attention on strategies for enhancing teacher quality. This attention makes sense, as a growing body of evidence points to the overriding importance of teachers in promoting student achievement. On average, students with a teacher in the top quartile of the talent pool achieve at levels corresponding to an additional two or three months of instruction per year, compared with peers who have a teacher in the bottom quartile.
Putting these numbers in context, this quality differential represents well over a third of the “achievement gap” between students from low-income families and those from families with higher incomes. Thus, consistent assignment to high-quality teachers can substantially lower the barriers to realizing academic success imposed by poverty. In contrast, class size reduction, a popular and expensive policy option, shows much less promise, if any, for addressing achievement gaps.
Because teacher quality is so critical to students’ success in school, gross inequity in the distribution of highly effective teachers should trouble policymakers. If students attending high-poverty schools are far less likely to be assigned effective teachers than students living in more affluent communities, then it would be a pressing matter to increase access to such teachers for economically disadvantaged students. Progress on this issue requires a careful look at the composition and dynamics of the teaching workforce.
A school’s teaching staff is not static. Teachers come and go, and the patterns of their movements between schools and into and out of the profession have undergone radical changes over the past 50 years. Researchers have begun to get a grip on these patterns and their relationship to teacher quality. This report focuses on three pieces of the puzzle: the distribution of teacher quality, teacher turnover, and tenure policies. In other words, who teaches where, who stays and who leaves, and how do tenure policies affect the decisions of teachers and the school districts that employ them?
The report is organized as follows. The first section explains how teacher quality can be measured. The very idea that teacher quality can be measured has its detractors. Some argue, on principle, that teaching is an art or a kind of sacred act that cannot be measured in any way that respects the scope or importance of the work. This point of view, however, does not hold much water in the globally competitive economy, where students need well-developed cognitive skills and where teachers, who are meant to help students develop these skills, absorb the majority of spending on public education. Historically, however, the business of measuring teacher quality has been problematic. The characteristics of teachers that are tracked most carefully are those traditionally important in hiring decisions and compensation systems (e.g., academic major, advanced degrees, years of experience). The term “qualifications” is adopted here to refer to these characteristics, which one estimate finds together explain only about 3 percent of the variation in student achievement. The rise of information technology and the recent boom in state-sponsored achievement tests, largely in response to accountability programs, have afforded researchers and policymakers access to better measures of teacher quality. These so-called “value-added” measures of teacher effectiveness have important limitations, but they hold promise for informing policies that address any inequitable distribution of effective teachers.
The second section explores the distribution of teacher quality. Although qualifications explain only a few percent of the variation observed in student achievement, they provide a reasonable basis for documenting systematic inequity in the distribution of teacher quality. Furthermore, qualifications will remain important in hiring decisions and compensation systems for the foreseeable future. An abundance of evidence suggests that the qualifications of teachers differ, on average, between high-poverty and low-poverty schools. These differences tilt in the expected direction. For example, students in high-poverty schools are less likely than students in low-poverty schools to be assigned a teacher deemed “highly qualified” under the provisions of the No Child Left Behind Act.
The third section examines teacher turnover. The term turnover encompasses mobility—teachers leaving one school for another—and attrition, which is defined as teachers leaving the classroom to take up other professional responsibilities, inside or outside of education, or to spend more time with their families. Mobility and attrition are con- founded by teachers returning to the classroom after several years away, a group that includes up to a fourth of newly hired teachers. Some turnover is inevitable; some is desirable. Chronically ineffective teachers should seek employment elsewhere. Instead of leaving the profession, however, such teachers may simply seek a school where their weak performance is less conspicuous. Attrition and mobility of effective teachers exacerbate inequity in the distribution of teacher quality.
The fourth section examines tenure, a term denoting the contractual or statutory job protections conferred on teachers who have completed a provisional phase of employment. Once tenured, a teacher’s employment may only be terminated for cause, and only after prescribed due process procedures have been followed. Tenure began as a countermeasure to various forms of employment discrimination, but successive waves of civil rights legislation have largely usurped this role. This section surveys what little is known about how tenure policies affect the distribution of teacher quality.
The last section concludes the paper by making the case that tenure embodies an important policy lever that ought to be explored. Right now, a good deal of evidence suggests that earning tenure is unrelated to what we value in teachers: their performance in the classroom. In particular, whether teachers can further student achievement is almost completely unrelated to the tenure decision. Given the interplay between teacher turnover, tenure policies, and the distribution of teacher quality, it is worth discussing what role changes in tenure policy could play in efforts to afford low-income students more access to effective teachers.
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