This paper presents findings of the longitudinal School Success Study (SSS), which is being conducted to determine the academic and social effects of nongraded (multiage, continuous progress) programs on Tennessee elementary school students. Covering the years 1993-99, the research seeks to identify successful school practices in both nongraded and graded programs. The study includes elementary-age students (K-4) from seven Tennessee schools that are implementing nongraded programs (n=1,500), three of which also have students in traditional classes (n=750), and five comparison schools in which all students are enrolled in single-grade classes. Academic achievement is measured by the Tennessee Comprehensive Assessment Program (TCAP) and the Tennessee Holistic Writing Assessment. Social development (academic self-concept) is measured using the Self-Concept and Motivation Inventory (SCAMIN). A one-way analysis of variance (ANOVA) indicates that students from nongraded classes during the first year of the study significantly outscored those from traditional classes on: (1) the grade 2 and 3 TCAP in vocabulary, total reading, total language, and total math; and (2) the third- and fourth-grade Holistic Writing Assessment. The SCAMIN analysis showed significant differences among students between various schools; however, the SCAMIN at this point is being used only to provide a baseline for the first student cohort. Four tables are included. Contains 33 references. (LMI)