New assistant principals find their new leadership role quite different from their previous work as teachers. This book, based on a 5-year study, addresses the realities of day-to-day life for new assistant principals (APs) in secondary schools. The book presents the actual experiences of men and women who made the transition from teacher to administrator. Data were collected through formal and informal conversations held with approximately 90 first-year secondary school APs in California, Washington, and Nebraska during 1989-94. The first chapter sets the scene for the book by describing the experiences of a new assistant principal, based on a diary kept by a beginning AP during her first year at a junior high school. The second chapter describes the importance of the assistant principalship as the entry to administrative careers and explains the book's purpose. Each of the succeeding chapters trace a different theme in the new AP experience. Chapter 3 describes how measures of time and duty differ from those in the classroom. Chapter 4 describes adjustment to the most dominant feature of an AP's life--the administration of student discipline. The fifth chapter describes the redefinition of relationships with former colleagues. Working with classified staff and other administrators is the focus of chapters 6 and 7. In the eighth chapter, new APs describe the emotional impact of their experiences. The final chapter uses research on APs, organizations, and organizational sociology to explain four of the most common themes in the APs' experiences. These four themes include: (1) Most beginning APs did not understand the nature of the assistant principalship; (2) new APs often lacked skills necessary to the job; (3) the AP position did not prepare APs to become principals; and (4) becoming an AP brought professional and personal changes. The afterword discusses the value of this information to various stakeholder groups. The appendix contains methodological notes. (Contains 152 references.) (LMI)