Since 1970, essentially all research favors the creation of small high schools. Four forces that have contributed to the growing obsolescence of large, comprehensive high schools are the onset of the information age, the emergence of an adolescent culture, the students' rights movement, and changing attitudes about the proper functioning of organizations. Two reform responses have emerged: breaking up existing big high schools into small schools within schools (SWASs) and creating new, small high schools. The two alternatives represent very different models of schooling with very different cultures. Successful examples of the SWAS approach are rare. Five types of error committed in designing them are errors of size, continuity, autonomy, time, and control. As a result, they rarely get much smaller than 400 students, the minimum size at which the familiar top-down hierarchy that accompanies big buildings still works. However, a smaller size is necessary to enable significant changes in teaching and learning. This is evidenced by the success of the new, small high schools, which diminishes when they get much larger than 200 students. Thus, there is a no-man's-land of school size between 200 and 400 students in which neither the factory model nor new forms of schooling work. School districts should foster ongoing conversations among like-minded teachers, parents, and students to develop new visions of the high school. As enrollments grow, they can trigger the piecemeal construction of small buildings that allow each group to realize its vision. (Contains 58 references.) (TD)