The purpose of this study was to evaluate the effect of an intervention utilizing modified schema-based instruction (MSBI) on the mathematical problem-solving ability of elementary school students with mild to moderate disabilities. Four participants were taught to solve percent of change word problems, which required them to calculate the discounted price of an item or service after the use of a coupon or the final price of an item or service after leaving a tip. Participants were then required to count out an appropriate amount of money to cover the final cost. Effectiveness of the intervention was measured by how many steps on a task analysis the participants were able to complete correctly. Results of the single-case, multiple baseline across participants design indicated a functional relationship between the intervention and the problem-solving ability of the participants. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]