In the past 30 years, research has suggested the need for much smaller high schools. In response, some administrators have attempted to subdivide big high schools into smaller entities. This digest reviews recent research on the movement to break up large schools and discusses five types of error common to such attempts--errors of autonomy, size, continuity, time, and control. Large high schools have frequently been broken up into schools within a school (SWAS) serving 200-500 students. This strategy attempts to personalize the familiar comprehensive high school, but characteristics built into the design of most breakup efforts make it impossible for the SWAS to develop a small-school culture. Five common errors bar many schools from crossing the big/small cultural divide: (1) longstanding big-school traditions and overarching functions undermine SWAS efforts to build their own identities; (2) SWAS are planned to be large enough to have individual principals, but this size ensures that the faculty will be too big to socially construct the vision of the new, small school; (3) specialized programs and experiences segregate younger students from older ones and create more transitions for student to accomplish; (4) traditional schedules prevent a personalized, spontaneous response to an unexpected learning opportunity; and (5) the big building that houses multiple SWAS continues the old control issues of the big school. (Contains 20 references.) (SV)