In recent years, the large comprehensive high school has been a subject of growing critique by researchers and reformers. "Factory model" schools have been criticized for their impersonal structures, fragmented curricula, segregated and unequal program options, and inability to respond effectively to student needs. Some studies have found that, other things equal, smaller schools appear to produce higher achievement, lower dropout rates, lower rates of violence and vandalism, more positive feelings about self and school, and more participation in school activities. These outcomes appear more pronounced for students who are traditionally lower achieving. In addition, the belief that large schools are necessarily more cost-effective has been challenged by studies finding equivalent operating costs and lower costs per graduate in smaller schools. However, there are competing findings about the effects of smaller schools for different groups of students and about the effects of school size and organizational features in diverse contexts. This review examines these findings across a wide range of studies over the last thirty years. The authors conclude that the influences of size appear to be mediated by other features of school organizations that are sometimes, but not always, associated with size, making the relationship between school size and many desired outcomes an indirect one. (Contains 140 notes.)