This paper describes: the development and implementation of Schoolwide Projects (SWPs) in the School District of Philadelphia (Pennsylvania); evaluation models permitted by Chapter 1 regulation and policy; ways these models were used in Philadelphia and results that were obtained; and approaches that are sensitive to the effects of SWPs. The initial implementation of the accountability provisions created by the 1988 reauthorization legislation is analyzed in depth. The impact of the different methods and their technical adequacy, and conclusions and implications for the 1993 Chapter 1 reauthorization are discussed. The study population consisted of Cohort 1 SWPs, whose accountability cycle began in the 1988-89 school year. The preprogram period spanned the school years 1985-86 to 1987-88; program years covered 1988-89 through 1990-91. The student participation information was obtained from the local education agencies' Chapter 1 Evaluation and Reporting System, which includes the data elements of school location, achievement test scores, and Chapter 1 services received. The techniques of maximizing aggregation while minimizing aggravation and other schools comparison analyses (non-proportional and proportional selection) were used. Various evaluation models permitted by the regulations produced markedly different conclusions about the effectiveness of SWPs. The evaluation models that were most likely to detect improvement in student achievement at a SWP site compared SWP students with Chapter 1 students at non-SWP sites during the same 3-year period. The weakest model compared SWP schools with their performance during the 3 years prior to implementation of the SWP. Fourteen data tables, 4 bar graphs, and a 19-item bibliography are included. (RLC)