Student mobility is the phenomenon of students in grades K-12 changing schools for reasons other than customary promotion from elementary school to middle school or from middle school to high school. This non-promotional school change can occur during the school year or in the summer between school years. It may involve residential change, school change, or both. Students may change schools for reasons that are considered positive, such as when a family moves to a better school, neighborhood, or job. In fact, the current education policy environment sends a strong message to parents that school choice--which typically involves school change--is good. Community-based charter schools and school voucher programs are examples of school choice policy initiatives. The federal No Child Left Behind Act of 2001 (NCLB) requires that school districts provide students in schools identified as "In School Improvement," based on trends in proficiency test passage rates, with the opportunity to transfer to a school not designated as "In School Improvement." Student mobility has consequences for schools, students, communities, and public policy. Research has found that students who change schools more frequently are likely to have worse educational outcomes. Highly mobile students are also more likely to be those with other risk factors--low income, special education, homelessness, or an unstable home environment. School changes worsen the learning and achievement problems of these at-risk children. In 2011, Community Research Partners (CRP) and The Thomas B. Fordham Institute (Fordham) entered into a partnership to conduct research on student mobility in Ohio. Fordham, a national leader in advancing educational excellence through quality research, commentary, and advocacy, wanted to build on their recent research on student mobility in the Dayton area and examine student mobility throughout the state. CRP brought to the project its experience in undertaking research on student mobility in the Columbus City Schools (CCS) and in processing and analyzing student-level records from the Ohio Department of Education (ODE). The research employs descriptive and analytic statistics--presented in spreadsheets, visualizations, and reports--to provide a picture of student mobility for all Ohio public school districts and buildings and public charter schools, with in-depth analysis for five large urban regions (Columbus, Cleveland, Cincinnati, Dayton, Toledo). The research also addresses several state policy issues of interest to Fordham: (1) open enrollment patterns; (2) "non-counters" profile (students whose test scores do not count in district performance ratings), and (3) monthly enrollment profiles of public districts. Appended are: (1) public school districts of each urban region; (2) public school buildings of each urban region; and (3) public charter schools of each urban region. Tables, figures, and maps are included in each urban region analysis. [Additional funding for this paper was provided by the Siemer Institute for Family Stability, Nord Family Foundation, KidsOhio.org, School Choice Ohio, United Way of Central Ohio, and United Way of Greater Toledo.]