This paper evaluates the impact of exposure to a voucher program for disabled students in Florida on the academic performance of disabled students who remain in the public school system. The authors utilize student-level data on the universe of public school students in the state of Florida from 2000-01 through 2004-05 to study the effect of the largest school voucher program in the United States, the McKay Scholarship Program for Students with Disabilities (McKay), on achievement in math and reading by students who have been diagnosed as disabled and remain in the public school system. The report is an empirical evaluation of the impact of exposure to a voucher program designed to allow students with disabilities to enroll in schools other than their local public schools on the achievement of disabled students who remain in their local public schools. Vouchers for disabled students are the fastest-growing type in the United States. Programs similar to McKay are currently operating in Ohio, Georgia, and Utah and have been recently considered by other states. Highlights of the study include: (1) Public school students with relatively mild disabilities made statistically significant test score improvements in both math and reading as more nearby private schools began participation in the McKay program, contrary to the hypothesis that school choice harms students who remain in public schools; (2) Disabled public school students' largest gains as exposure to McKay increased were made by those diagnosed as having the mildest learning disabilities; and (3) Academic proficiency of students diagnosed with relatively severe disabilities was neither helped nor harmed by increased exposure to the McKay program. (Contains 7 endnotes and 6 tables.)