The quality of student/teacher interactions, in effect, the quality of learning, is greatly affected by the qualities (characteristics, qualifications, attitudes, and skills) of teachers. The Schools and Staffing Survey (SASS), conducted by the National Center for Educational Statistics, collected information that enables an analysis of teacher qualifications and the proportion of students being taught by less than fully qualified teachers. This document presents four analyses of teacher qualifications using data from the 1987-88 SASS and the 1990-91 SASS. All four analyses look at the interaction of academic preparation in the field taught and certification to teach in that field. The first two analyses focus on teachers' qualifications to teach in their main assignment field, or the field in which they teach the most classes, while the final two analyses focus on secondary teachers' qualifications to teach individual subjects they are assigned to teach during the school day. Each analysis then yields a table showing whether or not the teacher is certified in the field, and whether or not he or she has academic preparation in the field. Data for each of the four cells generated (certified, prepared; certified, not prepared; not certified, prepared; and not certified, not prepared) are provided. (LL)