The Schools and Staffing Survey, 1990-91 (SASS 90-91), is a study that is part of the Schools and Staffing Survey (SASS) program; program data is available since 1987-88 at https://nces.ed.gov/surveys/sass/dataproducts.asp. SASS 90-91 (https://nces.ed.gov/surveys/sass) is a cross-sectional survey that covers a wide range of topics from teacher demand, teacher and principal characteristics, general conditions in schools, principals' and teachers' perceptions of school climate and problems in their schools, teacher compensation, district hiring and retention practices, to basic characteristics of the student population. The survey was conducted using mail, paper questionnaires, and telephone interviews. Teachers, librarians, principals, and school coordinators were sampled. Key statistics produced from SASS 90-91 are average teacher salaries and the percentage of teachers by teaching field.