The increasing role of schools in promoting financial literacy underscores the need to investigate the effectiveness of school-based financial education programs. This study examined FutureSmart—a free, co-curricular, online financial education course—using a quasi-experimental design with a diverse sample of middle school students nationwide. The study assessed the impact of the course on students' financial knowledge, attitudes, and behaviors, and explored the association of program implementation factors with changes in student outcomes. Financial knowledge gains were significant, substantial, and consistent across student subgroups and implementation factors for FutureSmart participants. Gains in financial attitudes and behaviors—specifically, financial confidence, engagement with parents about financial issues, current engagement with financial products, and intended future engagement with financial products—were not significant. The fundamental implication of this research is that FutureSmart effectively conveys financial knowledge to middle school students, contributing to a foundation for their future financial well-being.