Although the creation of the course schedule is one of the first and most important tasks undertaken to begin each school year, recent research has demonstrated that the scheduling process is often fraught with inefficiency and difficulties for teachers and students, difficulties that have been hypothesized to influence student outcomes negatively. This article extends this research by examining the degree to which students' grades are affected by a set of changes and disruptions--referred to as turbulence--that many students experience at the beginning of the school year. Using data from a large urban school district, the analyses of this article first demonstrate the existence of turbulence and document its widespread prevalence in the first year of high school. The impact of turbulence is then examined at two points in ninth grade, with results showing that in both the grades students receive in the first grading period and in their final year-end grades, students who experience more turbulence receive significantly lower marks. These analyses also point to a threshold effect, in which students who encounter some disruptions have somewhat lower grades while those who experience more have substantially lower grades. In the final section of the article, a multilevel examination of school-level factors related to turbulence reveals that, consistent with organizational theory, a substantial portion of between-school differences in turbulence are related to higher levels of student variation and turnover.