Standard errors for the average years of high school study required for graduation in selected subjects, and percentage of public and private schools that had a community service requirement, by sector and private school type: 1999–2000

*Restricted to schools that grant high school diplomas (district data on requirements were applied to public schools). Columns 1-4 were further restricted to schools reporting for 3- or 4-year high school programs, and columns 5 and 6 to schools reporting for 4-year high school programs.

SOURCE: U.S. Department of Education, NCES. Schools and Staffing Survey (SASS), "Public School District, and Public, Public Charter, and Private School Surveys," 1999–2000.