Money matters in education, especially for students from families that are struggling financially. Increasing school funding not only leads to improved school completion rates and higher achievement in low-income school districts, but over the long-term it can increase educational attainment, wages, and family incomes for children from low-income families. While the benefit of investing additional resources in schools serving low-income students is well-established in research, it is often ignored or not well understood by policymakers. This brief provides the research evidence advocates need when confronted with a fundamental question in the education policy debate: "Why should states invest additional resources in low-income students?"