In the past few years, political, economic, and social conditions in Ontario have changed rapidly. In some regions unexpected shifts in population have adversely affected school organization, and schools have had to be opened or closed in haste. This study has a twofold aim: to develop a methodology that will enable Ontario school boards to make demographic projections in support of educational planning, especially in regard to language of instruction, denominational character, and the educational needs of various socioeconomic groups; and to apply the methodology specifically to the Stormont, Dundas, and Glengarry County Roman Catholic Separate School Board. Conventional quantitative demographic methodology is complemented by structured interviews to investigate the general socioeconomic circumstances of the region and the decisions that families make in regard to school enrollment. The methodology is then applied to the projection of enrollment in a school board where the three factors (language, religion, and social class) affect attendance rates. This board, which seems to be experiencing enrollment fluctuations, covers both rural and urban areas. It offers what are known as "regular" and "adapted regular" programs to Francophone students, and "core" and 50/50 immersion programs to Anglophone students. The report's four chapters respectively provide an introduction, present the study methodology, illustrate the methodology by applying it to a particular school board, and finally present a summary of demographic observations and a critical review of the approach adopted. (34 references) (MLF)