In multigrade instruction, children of at least a 2-year grade span and diverse ability levels are grouped in a single classroom and share experiences involving intellectual, academic, and social skills. "The Multigrade Classroom" is a seven-book series that provides an overview of current research on multigrade instruction, identifies key issues teachers face in a multigrade setting, and offers a set of resource guides for multigrade teachers. Book 1 synthesizes research findings that compare multigrade and single-grade elementary classrooms with regard to various cognitive and noncognitive outcomes. Quantitative studies of academic achievement and student attitudes indicate that the multigrade classroom does not negatively affect students' academic performance, social relationships, or attitudes. Multigrade students do particularly well on measures of student affect. Qualitative studies of multigrade classrooms point to principal leadership, teacher beliefs, school climate, and sufficient time and money as essential ingredients for success. A table outlines what teachers and administrators need to know about multigrade instruction, and steps are listed for setting up multigrade classrooms. Classroom, school, and sociocultural factors unique to rural, small schools are listed. Studies involving multigrade instruction are reviewed. Key variables affecting multigrade teaching and administrative concerns are identified. (Contains 67 references.) (SV)