The amount and quality of time available for instruction were studied in the Chicago, Illinois, public schools. The report focuses on the basic structures of time and how teachers use them to create learning opportunities for their students. Data are from a 3-year series of school and classroom observations from 1994 to 1996 made in 8 elementary and 7 high schools. The team of researchers observed more than 200 teachers and more than 1,000 periods of instruction. School time was coded as a series of activity segments, and these were analyzed to develop descriptive accounts of how time proceeds through the school year. The analyses demonstrate that the problem of not enough time is a cumulative result of many issues, each of which requires its own redress. Isolated workshops on time management are not the answer. Instead, teachers need integrated programs of teacher development in the context of a school-based professional community. In addition, to deliver quality instructional time, teachers must have some noninstructional buffer zone that absorbs the logistical and managerial demands of school life and the personal and social needs of children. Observation of skilled teachers indicates that 20 to 25% of the school day must be seen as serving these functions. Therefore, to have 300 minutes of instruction in a school day, the day must be 360 to 400 minutes long. Taking the problem of instructional time seriously may be one of the most powerful basics the school system and community can support. (Contains 6 figures, 31 endnotes, and 55 references.) (SLD)