RAND has tackled the practical problem of cost-effectiveness with its latest Microworld effort, ESSCOTS (Educational Support Systems based on Off The Shelf software). Despite its complex acronym, ESSCOTS is a simple approach to educational software design. In the software market today there are scores of high-tech programs for scientific, industrial and commercial uses. Though they are powerful tools for engineers and other specialists, their complexity makes them out of reach and undesireable for K-12 educational use. But if support software could be designed to adapt these programs for basic, yet intelligent educational purposes, the startup costs for producing effective educational tools would be greatly reduced.