Funding for California's schools has reached record-high levels, although the pandemic has exacerbated longstanding inequities in student outcomes. As policymakers grapple with questions around how much to fund schools and how that funding should be distributed, existing research can provide insights into where and how to use additional funds to improve outcomes. This review of the research revealed several themes: (1) Several years of sustained spending increases improved student outcomes; (2) How--and to whom--spending is targeted matters; (3) The labor market for educators may constrain spending policies and create tradeoffs; and (4) Cost pressures in California schools affect the efficiency of funding. [Research support for this document was provided by Joseph Herrera. For the Policy Brief, see ED623531. For the technical appendix, see ED623533.]