Chicago has been in the forefront of the country in its use of 9th-grade indicators of dropout. Catalyzed by the development of the freshman on-track indicator and research around it, Chicago school administrators, central office personnel, and external partners have developed a number of mechanisms using 9th-grade indicators to stimulate school improvement. This article describes 3 ways in which early warning indicators are useful for improving student achievement: (a) focusing conversations and efforts on actionable problems; (b) identifying students for intervention; and (c) using indicator patterns to address low performance in a strategic way. Examples from high schools in Chicago suggest that knowledge of the on-track indicator and its use in district accountability were not enough to change practice. However, the availability of data tools that make it easy to act on information about on-track rates have changed the ways in which teachers and school staff interact with each other, students, and parents regarding improving student performance. The strategies they have developed with the data tools have provided a systematic focus to their efforts, which appears to be paying off in substantially improved ninth-grade achievement. (Contains 1 table, 4 figures, and 11 footnotes.)