This document provides the final summary report of Tennessee's primary school class size study, called Project STAR. Sections of the report concern: (1) background; (2) organization to conduct the study; (3) sample selection; (4) data collection plan and data base; (5) general operating guidelines; (6) teacher orientation; (7) study design; (8) choice of within-school design; (9) selection into the three conditions; (10) modifications in study design; (11) primary analysis methodology; (12) achievement results; (13) noncognitive results; (14) acheivement results based on effect size; (15) the effect of small classes on grade retention; (16) the effect of inservice teacher training on student achievement; (17) teacher grouping practices; (18) parent/volunteer-teacher interaction; (19) teacher problems; (20) teacher exit interview data; (21) the impact of reducing class size on cost effectiveness; (22) estimates of the magnitudes of the differences for kindergarten through grade three; and (23) conclusions. A fact sheet on the study emphasizes that the smaller classes made the highest scores on the Stanford Achievement Test and Basic Skills First Test in all four years (K-3) and in all locations (rural, suburban, urban, and inner-city). Teachers must have particular characteristics and possess certain skills for class size reduction to be optimally cost effective. Thirteen tables supplement the text. (RH)