Effects of teacher-pupil ratio on kindergartners' mastery of reading readiness objectives were studied. The study was part of Tennessee's Project STAR, a 4-year study of class size. About 2,850 students in 38 elementary schools that served 4 types of communities: innercity, suburban, urban, and rural, in 26 Tennessee school systems participated. Basic reading skills objectives were divided into three strands: word identification skills, comprehension skills, and reference and study skills. There were three categories of classes: small, regular, or regular with full-time teacher aide. Data were collected from individual or group profiles indicating mastery or nonmastery of objectives tested. Data were analyzed with a five-way analysis of variance and a cross-tabulation procedure with a chi-square test of significance. Findings suggested that class size was a significant factor in kindergarten reading readiness achievement. Small classes achieved greater mastery on 25 Basic Skills First objectives and 20 comprehension objectives, but not on 5-word identification objectives. Students who did not receive free lunches outscored students who received free or reduced cost lunches in every comparison. Innercity students obtained the lowest scores of the four geographic localities. Students in the lowest attendance category obtained the lowest average scores in each of the three class size conditions. (RH)