For years, Marilyn Arons, 67, has taught parents how to use the main federal special education law to get the most appropriate education for their children. And now, the role of experts such as Ms. Arons is at the center of a U.S. Supreme Court case that will be heard next week. The case, which began in 1997, involves New York state's Arlington Central district of more than 10,000 students, which includes part of the town of Poughkeepsie, and eight other towns in the Hudson Valley. Pearl and Theodore Murphy battled the district over the (Individualized Education Program) IEP for their son, Joseph, now 22, who has multiple learning disabilities. The Murphys successfully argued that the district should pay for his private school tuition. During the due-process proceedings, the parents relied on the expertise of Ms. Arons.