In Illinois, 25 districts have interim superintendents this year. Of the state's 871 districts, 159 have new leaders, compared with about 80 a decade ago. Officials expect another 100 or more new openings will be filled next year. Across the nation, school boards face increasingly shorter lists of interested candidates for superintendent openings, and districts must pay more for top-tier candidates because they are in such high demand. Many professionals say the crushing demands of the job -- from harassing calls from parents to pressure to meet federal education mandates -- have become a major deterrent.