The National Association of Secondary School Principals periodically studies practices and characteristics of secondary schools to help inform educators and shape policy. Such studies of middle-level education were conducted in 1966 and 1981. As middle-level education moved into the 1990s, many new questions about education and leadership needed to be asked and old ones revisited: What are the differences in views and preparation of school leaders? Has middle-level school leadership changed? Has the "leadership team" concept emerged? And what middle-level school programs are successful? This study examines these questions by asking middle-level school principals, assistant principals, and leadership team members about personal characteristics, job roles and tasks, and professional beliefs. Also examined are programs, practices, and trends in middle-level schools. Information from this survey of 2,000 middle-level schools in the 1991-92 school year is presented and compared, where applicable, with findings from six previous surveys going back to 1966. In addition to an introduction, this study includes chapters on personal and professional characteristics, school leadership, educational programs, issues and trends, and leadership profiles. An appendix includes sample questionnaires used in the survey. (Contains 34 references.) (JPT)