The More Effective Schools project, an effort to make the schools better able to solve the basic reading and arithmetic problems of disadvantaged children, brought about a reorganization and expansion of the teaching and administrative staffs of elementary schools in New York City. The combined black and Puerto Rican population in the project schools was greater than 50 percent of the total school population, and all classes (preK-6) were heterogeneously grouped. Class size was reduced, after school study centers were opened, team teaching and other innovations were introduced, and teacher specialists were used. Benefits claimed in reading and arithmetic achievement as measured by standardized tests are conflicting because of the variety of designs used to evaluate student performance. Several interpretations of the data are included in this report, as well as information on staff, program methodology, and costs. (EF)