Class size may be important in achievement, but it is not the only decision for policymakers. Class size plays a role, but the role is effectively fulfilled only when the other players are successful. Therefore, it is appropriate to address several questions: What goals are to be accomplished; what is the best distribution of personnel related to these goals; what roles do curriculum, instruction, time, and home support play; and how do the personnel work together effectively to achieve those goals? In the broadest sense, the fundamental question is: How are decisions made? For the sake of discussion, three levels of decision making related to class size are presented. Generally speaking, there are three broad categories or levels: (1) Professional and public opinion; (2) A critical analysis of educational research evidence; and (3) A decision-making process. The premise of this article is to provide some rationale and ideas regarding how policymakers can move through the more sophisticated levels of the taxonomy--the critical analysis of educational research evidence and a structured decision making process. This article is divided into three parts. In the first, "Does Class Size Make a Difference: A Brief Overview of the Research," a sampling of studies is presented. The second section is titled, "How Much of a Difference Does Class Size Make on Achievement?" The 1978 meta-analysis of Glass and Smith suggested the possibility that achievement increases faster as class sizes become smaller. The third and final section closes with some observations. (Contains 3 figures, 9 tables, and 11 endnotes.)