School Development Plans (SDPs) were pioneered by individual schools and local education authorities (LEAs) in England as a grassroots approach to school management that was eventually adopted by national education authorities. An empirical investigation of the implementation and impact of SDPs was carried out in primary schools through a combination of qualitative and quantitative data collection. With the cooperation of administrators of urban and rural schools, a questionnaire was prepared on attitudes and support for school development planning. This questionnaire, sent to 110 LEAs in England, 12 in Scotland, 8 in Wales, and 5 in Northern Ireland, obtained a 100% response rate. Data were also collected in the schools through interviews and observation in nine case study schools. Results supported a typology that described SDPs as rhetorical, singular, cooperative, or corporate in nature. Only corporate plans, characterized by a united effort to improve and a sense of shared ownership, resulted in real educational change. The more effective the plan was, the more complex its characteristics. The aspect of SDPs that was found to be the weakest was that of formative evaluation, but schools engaged in the corporate type of planning were most likely to use formative evaluation to support the development process. (Contains 39 references.) (SLD)