Connecticut's interdistrict magnet schools offer a model of choice-based desegregation that appears to satisfy current legal constraints. This study presents evidence that interdistrict magnet schools have provided students from Connecticut's central cities access to less racially and economically isolated educational environments and estimates the impact of attending a magnet school on student achievement. To address potential selection biases, the analyses exploit the random assignment that results from lottery-based admissions for a small set of schools, as well as value-added and fixed-effect estimators that rely on pre-magnet school measures of student achievement to obtain effect estimates for a broader set of interdistrict magnet schools. Results indicate that attendance at an interdistrict magnet high school has positive effects on the math and reading achievement of central city students and that interdistrict magnet middle schools have positive effects on reading achievement. (Contains 20 notes, 8 tables, and 1 figure.)