While equitable funding of K-12 public school has become an acute issue in many states, Illinois ranks among the most inequitable in its mechanisms for dispersing revenues to school districts. Illinois property taxes are the primary means for financing schools. However, due to very low state general aid, many property owners pay very high property taxes to support their schools. Consequently, the need for increased state support comes at a time when legislators have repeatedly proposed to freeze property taxes permanently, or for two to four years. Additionally, statewide bills have been introduced since 2012 that would shift pension costs, currently picked up by the state (excluding Chicago), to school districts. This research report from the Project for Middle Class Renewal in the School of Labor and Employment Relations at the University of Illinois, Urbana-Champaign examines the relationship between school revenue and achievement levels in Illinois. We first examine data on local school districts from 2011-2012 to 2016-2017 to explore and illustrate how revenue and expenditures vary by rates of low-income students and other key indicators. We find at the district level, higher instructional spending is associated with statistically significant improvement in aggregate student proficiency levels, after controlling for disadvantage and other characteristics at the district level. This positive relationship generally parallels the findings of recent studies that have concluded that money does in fact matter for education.