Boosting high school graduation rates is a growing concern to educators and policymakers. Researchers stress that, although graduation rates have varied little in recent years, "[w]hat makes current graduation rates alarming is a reality of the new U.S. economy: It is practically impossible for individuals lacking a high school diploma to earn a living or participate meaningfully in civic life." Research shows that students who fail to graduate high school exhibit clear signs of dropping out. Warning signs such as irregular attendance, poor academic performance, behavior problems and grade retention are more precise predictors of whether a student will ultimately drop out than are social and economic indicators such as family income and parental involvement. States have made notable progress collecting longitudinal information that follows individual students over time. Access to such student data has prompted state and school district officials across the country to develop "early warning indicator systems" to efficiently identify students who are at risk of dropping out and provide targeted supports to get them back on track and graduate. This paper provides summaries that highlight the statewide early warning indicator systems in Louisiana, South Carolina, and Alabama and the Philadelphia Public Schools district-wide system. (Contains 19 endnotes.)