The Schools and Staffing Survey (SASS) of the National Center for Education Statistics provides periodic, timely data on public and private elementary and secondary schools in the United States. Data collected include: school and teacher characteristics; school operations, programs, and policies; teacher demand and supply; and the opinions of teachers and administrators about policies and working conditions. Data are collected through seven surveys conducted during the same school year. This report documents the sample design and estimation procedures for the third SASS collection, conducted in 1993-94, in which 13,000 schools and administrators and 67,000 teachers were selected. In addition, 5,500 local education agencies associated with selected schools and 100 districts not associated with selected schools were studied. Some 7,600 school libraries and librarians and 6,900 students were also surveyed. The report describes: (1) school and teacher sample stratum allocation; (2) overlapping 1991 and 1994 SASS samples; (3) public school and principal sample design; (4) local education agency sample design; (5) private school and principal sample design; (6) teacher sample design; (7) public and private school library and librarian sample; (8) public and private school student sampling design; (9) weighting; (10) imputation; (11) variance estimation techniques; and (12) frame evaluation. Five appendixes present supporting data about data analysis techniques. (Contains 26 tables, 35 figures, and 20 references.) (SLD)