The extent to which school buildings support education has been an important topic for policymakers. One issue is the physical condition of the buildings, particularly as school buildings age. Another is the ability of the buildings to accommodate shifts in the nation's population: some communities have experienced decreases in school-age population due to outmigration or shifts in the age distribution, leading to below-capacity enrollment in their schools, while others have experienced large increases in population and have needed to build new schools, expand existing ones, or put more students in buildings than the buildings are designed to serve. This report is based on a survey of school principals conducted by the National Center for Education Statistics (NCES) in the Institute of Education Sciences, U.S. Department of Education. It presents current information on the extent of the match between the enrollment and the capacity of the school buildings, environmental factors that can affect the use of classrooms and school buildings, the extent and ways in which schools use portable buildings and the reasons for using them, the availability of dedicated rooms for particular subject areas (such as science labs or music rooms), and the cleanliness and maintenance of student restrooms. The data were collected from mid-September 2005 through late January 2006 from public elementary and secondary schools in the 50 states and the District of Columbia. T-tests were used to test for statistical significance. Appended are: (1) Technical Notes; and (2) Questionnaire. (Contains 39 tables, 6 figures, and 2 footnotes.)