In 1993, the Campaign for Fiscal Equity (CFE) challenged New York State's school financing system on the grounds that it failed to provide students sufficient opportunity for a sound basic education in New York City. CFE prevailed in 2003, after the case went before the New York Court of Appeals, and the state's funding system was determined to be unconstitutional and ordered to be altered to ensure "adequate" funding. The final decision decreed that before any remediation take place, an objective study be conducted to determine how much it would cost to provide an "adequate" education for all public school students in the state, on which this article is based. Although a professional judgment approach forms the centerpiece of the work, components of the analysis draw on other methodological tools (i.e., public engagement, expert panels, and successful schools) to further support the results. We find that for a majority of districts significantly higher levels of spending are required if the state wishes to provide a sound basic education to all public school students. Furthermore, the results show a clear negative relationship between the district-level shortfall in spending and educational outcomes across virtually all student subpopulations.