This study demonstrates a method for extending debates on the effectiveness of school inputs into the cost-effectiveness realm. This study uses the example of Florida's statewide initiative to reduce class sizes to determine which of many state inputs buys the most effect for the same expenditure. The method includes a three-stage process: multiple regression to determine the effects of various inputs, cost analysis to attribute costs to each of these effects, and a simulation to compare relative costs. The benefits of extending effectiveness models into the cost-effectiveness realm are borne out by the results. Using data from 1,734 elementary schools in Florida, we found that class size and per-pupil expenditures in these schools are the least cost-effective means of raising test scores. (Contains 8 footnotes.)