This book investigates teaching practices before, during, and after reform impulses in the 20th century aimed at changing what teachers routinely do. Patterns of stability and change over a 90-year period are developed from evidence from a wide variety of sources, including classroom photographs, textbooks and tests used, student recollections, teacher reports of how they taught, and classroom observations by parents and administrators. A continuum stretching from teacher-centered instruction to student-centered instruction provides a tool to help map the intricate complexity of classroom practices. Part I covering 1890-1940 consists of three chapters: (1) a description of teaching at the turn of the century, including progressive reforms of that era; (2) case studies of classroom practices in New York City, Denver, and Washington, D.C. during the 1920s and 1930s; and (3) a survey of teaching practices nationally during those 2 decades, particularly in rural schools. Part II summarizes case studies of informal and open education in Washington, D.C., New York City, and North Dakota during 1965-1975, and provides an intensive look into Arlington (Virginia) classrooms during 1969-1980. Part III examines five possible explanations for continuity/change in teaching during this century: (1) school as a form of social control and sorting; (2) constraints related to the organizational structure of school and classroom; (3) the culture of teaching; (4) individual and shared beliefs about child development, the role of school, and authority; and (5) the nature and effectiveness of reform implementation. This book contains over 300 references, many photographs, and an index. (SV)