Each year, the federal government provides billions of dollars to support low-income schools through the federal Title I program. Most of this money goes to Title I schools operating schoolwide programs. Schoolwide schools have authority under federal law to use Title I funds--and in some cases, other federal funds--flexibly to upgrade their educational programs. This means that Title I can be used to support comprehensive initiatives that improve academic performance across the school. Few schools, however, take full advantage of schoolwide's program design options--often because of misunderstandings of a federal requirement known as the "supplement not supplant" rule. This limits the opportunity to use Title I as a resource to support school turnaround efforts. This toolkit provides an overview of the schoolwide program option, and describes how schoolwide schools can use Title I funds to support comprehensive reforms. In particular, it explores the "supplemental funds test" that applies to schoolwide schools, and explains how it differs from traditional supplement not supplant rules. Many states limit Title I spending options in schoolwide schools, often inadvertently. This toolkit provides considerations for states wishing to eliminate or streamline state-imposed barriers to the schoolwide model. It also provides considerations for school districts and schools that wish to use the schoolwide model more effectively.