This paper examines systematic ways in which school districts differ and the implications of these differences for how schools work and for the implementation of reform proposals. Data from the California State Department of Education and Florida State Department of Education were analyzed to examine the effect of organizational and resource variables on decentralization in school districts. Findings suggest that there is wide diversity among school districts with regard to autonomy and resources. District patterns of organizational structure are, to some extent, endogenous. In particular, school organizations facing different external political pressures adopt different structures, with consequent differences in patterns of influence. Districts in politically intense communities are likely to have lower returns on decentralization reforms. The degree of decentralization should be viewed in part as having evolved to respond to differences in the environment, including the political environment. These differences are likely to affect both the resistance to and the effectiveness of decentralization. Effective decentralization requires adaptation of its form and structure to reflect differences among districts. Five tables are included. (Contains 12 references.) (LMI)