This report provides a comprehensive review of the research on the effect of K-12 school funding on student outcomes. In other words, does money matter in education? This is the third edition of this review, with the first two editions having been published in 2012 and 2016. In the previous edition of this report, the authors reviewed the evidence on whether money matters for the performance of K-12 public schools. The conclusion, which was entirely unsurprising to educators, was that the research overwhelmingly suggested that adequate and equitable school funding is a necessary precondition for improving student outcomes. Some of these earlier studies, however, relied on insufficient data and methods, and they sometimes reached inconsistent conclusions. This led to confusion about and misrepresentation of what the research said. Since then, a steady stream of new studies, using even better data and more advanced statistical methods, have been published. In this updated edition, the authors review this newer evidence. They find, put simply, that it has not only settled the question of whether money matters (it does), but has also let new light shine through on key details, including the kinds of investments that matter, who benefits most from them, and the impressive magnitude and consistency of their impact.