Financial literacy and cognitive capabilities are convincingly linked to the quality of financial decision-making. Yet, there is little evidence that education intended to improve financial decision-making is successful. Using plausibly exogenous variation in exposure to state-mandated personal finance and mathematics high school courses, affecting millions of students, this paper answers the question "Can good financial behavior be taught in high school?" It can, though not via traditional personal finance courses, which we find have no effect on financial outcomes. Instead, we find additional mathematics training leads to greater financial market participation, investment income, and better credit management, including fewer foreclosures.