This longitudinal study helps to permit a better understanding of the impact that different life events have on teachers' careers (such as getting married, moving to a new location, or starting a family). It also provides some insight on how school and/or district characteristics and policies affect teacher satisfaction, and how teachers respond to transitions in their lives and careers (such as moving to a different school, changing the grade levels or subject taught, becoming a mentor, transitioning into a K-12 administration position, or exiting the teaching field). This survey contributes to policymakers' understanding of teachers and of teachers' careers as they enter, leave, or re-enter the teaching workforce and make important career and life decisions. The BTLS data can be used to answer numerous questions, including: Are beginning teachers who received formal mentoring from their school or district less likely to leave the profession or change schools in the first few years of their teaching career? Do mobility rates of teachers both within and outside of school districts change over time? Why do teachers leave the teaching profession and which factors have greater importance at various stages in teachers' careers and lives? What proportion of teachers return to teaching after a break in their teaching career? What motivating factors bring former teachers back to the profession?
The main sample design objective of the school survey was to provide estimates of school characteristics by the following key analytical domains: the nation; elementary and secondary levels for all sectors; public schools with a population of at least 20 percent American Indian or Alaska Native students; BIE schools at the national level; public schools by school level, region, and state; and private schools by school level, region, and affiliation strata. Another objective was to balance the requirements of the samples in the Schools and Staffing Survey (SASS). For each sampled school, all districts in the public sector, principals, and library media centers in the public and BIE-funded school sectors received questionnaires. The 2007-08 SASS sampled schools first, and then linked each school to its corresponding school district (or local education agency). To obtain a representative teacher sample, schools were more likely to be selected if there were a larger number of teachers within a given school, although schools of all sizes were sampled. Teachers within schools were then sampled at a rate of at least one and no more than 20 teachers per school, averaging between 3 and 8 teachers per school. The SASS sample design also sought to minimize selecting the same schools as other NCES school-based surveys.