A longitudinal study of the rate of growth of school districts' resources in large central cities in Illinois is presented. The data analyzed covered the years 1972-73 and 1981-82 and were derived from the State Board of Education and the 1970 and 1980 United States Census. The study looked at the changes in average daily attendance (ADA), changes in per capita and median family income, local dollars generated per ADA, and elasticity of effort based on equalized assessed valuation per ADA. The study concluded that a decline in fiscal capacity has occurred over the decade, but that school operating expenditures have not decreased. This is a result of increased state aid and some increases in local fiscal support. Noting that in some cases per capita income and median family income have increased faster than dollars locally raised per ADA, the study suggests that central city schools could be quickly plunged into financial difficulties if state aid cannot be sustained. Many schools appear to be slowly giving up their base of local financial support. The authors conclude that Illinois school districts not keeping pace with increases in per capita income need to carefully examine their fiscal health. The authors offer four legislative implications and recommendations for the future. (MD)