Struggling schools that come under increased accountability pressure face a number of challenges, changing instructional policies and practices to facilitate student improvement. But what effect does school accountability have on teachers' mobility decisions? This study is the first to exploit policy variation within the same state to examine the effects of school accountability on teacher job changes. Using student-level data from Florida State the authors measure the degree to which schools and teachers were "surprised" by the change in the school grading system that took hold in the summer of 2002--what they refer to as an "accountability shock"--by observing the mobility decisions of teachers in the years before and after the school grading change. Several key findings emerge: (1) over half of all schools in the state experience an accountability "shock" due to this grading change; (2) teachers are more likely to leave schools facing increased accountability pressure--and even more likely to leave schools that face the highest accountability pressure (schools shocked downward to a grade of "F")--and they are less likely to leave schools facing decreased accountability pressure; (3) While the quality differential between stayers and leavers does not change as a result of increased accountability pressure, schools facing increased pressure experience an increase in the quality of teachers who leave or stay and schools with no accountability shock experience no significant change to the quality of teachers that leave or stay. The results suggest if these schools were able to retain more of their high-quality teachers, perhaps through increased incentives to remain in the school, the performance gains associated with school accountability pressure could be greater than those already observed. (Contains 9 tables, 1 figure and 16 footnotes.)