This paper describes the school mobility rates for elementary and middle school students in North Carolina and attempts to estimate the effect of school mobility on the performance of different groups of students using student fixed effects models. School mobility is defined as changing schools at times that are non-promotional (e.g., moving from middle to high school). We used detailed administrative data on North Carolina students and schools from 1997 to 2005 and followed four cohorts of 3rd graders for six years each. School mobility rates were highest for minority and disadvantaged students. School mobility rates for Hispanic students declined across successive cohorts, but increased for Black students. Findings on effects were most pronounced in math. School mobility hurt the math performance of Black and Hispanic students, but not the math performance of white students. School mobility improved the reading performance of white and more advantaged students, but had no effect on the reading performance of minority students. "Strategic" school moves (cross-district) benefitted or had no effect on student performance, but "reactive" moves (within district) hurt all groups of students. White and Hispanic students were more likely to move to a higher quality school while Blacks were more likely to move to a lower quality school. The negative effects of school mobility increased with the number of school moves. Tables are appended. (Contains 1 exhibit, 9 footnotes, 5 figures, and 15 tables.)