This research brief reviews selected 1986 publications concerning the effects of class size on student achievement, attitudes, and behavior. The following points are made: (1) smaller classes in the lower grades have a positive effect on student learning attitudes and behavior; (2) minority, disadvantaged, and low-achieving students perform better in smaller classes; (3) lowering class size to 20 may have a positive effect on student learning, but lowering it only to 30 may not; and (4) while many positive results are believed to come from small classes, class size is but one of several variables affecting classroom climate and student achievement. (JAM)