"Turning around" chronically low-performing schools is of increasing interest to educators and policymakers, as highlighted by the U.S. Department of Education's (2010) recent call to rapidly improve the nation's 5,000 lowest performing schools. Yet there is little rigorous research on changes in student populations and teacher workforce in schools undergoing interventions to improve low-performing schools. To fill this gap, this study examines turnaround intervention models intended to rapidly improve student performance in chronically low-performing schools in the Chicago Public Schools district. It analyzes the changes in student populations and teacher workforce in 31 public schools in Chicago selected for district-led reform interventions for chronically low-performing schools over 1997-2010. Two research questions guided the study: (1) Did the characteristics of students change in the intervention schools?; and (2) Did the characteristics of teachers change in the intervention schools? For the first research question, descriptive analyses compared students in the school the fall before the intervention with students in the same grades in the fall after the intervention began. For the second, descriptive analyses compared the teacher workforce in these schools for the same periods. These descriptive analyses show school-by-school changes in students and teachers organized around the intervention models. The analyses are based on the entire population of students and teachers at each school and are not statistical estimates. Comparing student enrollment the fall before the intervention and the fall after the intervention shows that: (1) Twenty-three of 31 schools served fewer students by grade after the intervention, with five schools serving at least a quarter fewer students. Four of the schools with the largest declines in enrollment were part of the closure and restart model; (2) Except for schools in the closure and restart model, schools reenrolled 55-89 percent of students eligible to reenroll. The rates were similar to reenrollment rates in the years before intervention; (3) Schools in the closure and restart model reenrolled 0-47 percent of students eligible to reenroll. Schools in this model were closed for one or two years before opening again, did not serve all the same grade levels when they reopened, and held citywide enrollment lotteries, which made it difficult for students to reenroll; and (4) The composition of the student body--in race/ethnicity, socioeconomic status, and special education status--in intervention schools was largely similar before and after the interventions in all models except for the closure and restart model. In that model, schools after intervention served a larger percentage of economically advantaged students and of students with higher prior achievement levels, and smaller percentages of special education students and of students residing in the neighborhood near the school. Comparing the teacher workforce the year before the intervention and the year after the intervention shows that: (1) The extent of teacher rehiring varied with the intervention model. Schools in the reconstitution model rehired 42-66 percent of teachers, and schools in the STSP model retained 44-80 percent. Schools in the closure and restart, AUSL, and OSI models rehired just 0-24 percent of teachers; and (2) In all intervention models, the teacher workforce was more likely to be White, younger, and less experienced and more likely to have provisional certification after intervention than before it. (Contains 1 note.) [For the full report, "Changes in Student Populations and Teacher Workforce in Low-Performing Chicago Schools Targeted for Reform. Issues & Answers. REL 2012-No. 123," see ED531351.]