Running one of the nation's largest school districts typically comes with prestige and pay that draw would-be educational superstars, but also pressure and political complexity that cause them to burn out far faster than leaders of the majority of districts. A study published in the December issue of the American Educational Research Journal finds in 90 percent of 100 California districts studied, 43 percent of superintendents left within three years--but 71 percent of superintendents left the largest 10 percent of districts, which include those of 29,000 or more students, during that time. While superintendent turnover has not received as much focus from researchers or policymakers as teacher or principal turnover, stability at the central office has been linked to a greater likelihood of success for new education initiatives, which typically take five to seven years to mature. One analysis of more than 2,700 districts by the Denver-based Midcontinent Research for Education and Learning, or McREL, found that a one standard deviation improvement in the quality of a superintendent, as measured by researchers' criteria, was associated with a 9.5 percentile-point gain on state tests for the average district, and that student achievement growth was linked to longer tenures of district leaders.