Research studies on class size date back to 1900. Common sense has suggested that small classes lead to greater academic achievement, but most research on the effects of class size on achievement have been inconclusive. Furthermore, the financial costs and political consequences of reducing class size have generally prohibited the adoption of class size reduction alternatives. The Department of Education in the State of Indiana, however, has adopted Project PRIMETIME, which has attempted to reduce the class size in primary grades throughout the state. This document reports on the effect on student learning of reducing first grade class size to 18 students or fewer. Subjects for the studies were first-grade students in three elementary schools in Princeton, Indiana. Results of 13 studies, focusing mainly on basic reading and mathematics skills, provide overwhelming evidence of the gains in scores for students in the small-size classes of the 1984-85 school year as compared to the larger classes of the previous year. Four tables, one page of references, copies of the reading and mathematics evaluation systems, and a letter from the governor are appended. (IW)