Magnet schools hold a prominent place in the history of education reforms in the United States. Best known for offering unique programs or curricula to attract students from outside a school's neighborhood, many magnet schools started off as neighborhood public schools but converted with the goals of increasing student diversity and achievement. These goals remain important to policymakers and educators today, so there is interest in understanding what happens to converting schools, including those funded under the U.S. Department of Education's Magnet School Assistance Program (MSAP). This report describes the results of a descriptive study of 21 MSAP-supported elementary schools. The study collected data on these schools for several years before and after their magnet conversion, to see how their student body composition and academic achievement changed over time. The group of schools contained 17 that converted to become what might be called "traditional" magnet schools and another 4 that converted to become "destination" magnet schools. Key findings on the schools using the two conversion approaches include: (1) When measured against district changes, both types of magnet schools experienced some changes in diversity in the expected direction; (2) Achievement in the traditional magnet schools was higher after conversion, outpacing district changes in English language arts (ELA) but not in mathematics; achievement in destination magnet schools did not change, while their districts improved over the conversion period; and (3) There is not evidence that magnet conversion itself played a role in the study schools' diversity or achievement, with the exception of the decline in the concentration of minority students in traditional magnet schools. The following are appended: (1) Districts and Schools in the Study; (2) Use and Coding of Administrative Data; (3) Director Interviews; (4) Principal Survey; (5) Additional Data Sources; (6) Details of Analysis Methods; (7) Subgroup Analyses; (8) Sensitivity Analyses for CITS Findings; (9) Supporting Exhibits for Chapter 5; (10) Supporting Exhibits for Chapter 6; and (11) Analysis Methods and Supporting Exhibits for Chapter 7. [The following are acknowledged for contributions to the study: National Center for Education Evaluation and Regional Assistance; and Berkeley Policy Associates.]