Elementary and secondary students can be impacted by a number of risk factors, all of which can have a negative influence on their academic success. To that end, the identification of risk factors is an important first step in closing achievement gaps. For example, clear evidence of an achievement gap can be found in Indiana's high school graduation rate where, in 2009, 84.4% of white students graduated compared with 66% of African American students; 58.6% of students with disabilities; 61.5% of students with limited English proficiency, and 68% of students in poverty. This study took a longitudinal approach to the analysis, comparing the incidence of at-risk students in Indiana between 1999 and 2009. Unlike much previous research, this study utilized a research-based typology of risk factors to ensure accuracy and consistency over time. The article begins with a brief historical review of the research literature on the definition and identification of risk factors. In the second section, research methods and data sources are described. These are followed by the results of the analysis and conclusions. (Contains 9 tables, 1 figure and 20 endnotes.)