The report analyzes the influence of shifting enrollment patterns on the public school system. The research was undertaken in response to a request by the House Committee on Education and Labor for background material related to the Elementary and Secondary School Act. The report is presented in 12 major sections. Section I defines demography (the branch of the social sciences which deals with the determinants and consequences of population change), describes the format of the report, and presents summary observations. Section II explains the effect of birth and fertility rates on demographic trends and draws general implications of population projections for school enrollment trends. Sections III through XI present and interpret data relating to changing family patterns, working women, immigration, mobility, enrollment, responses to declining enrollment, teacher shortages, schools and students, private school enrollment, and effects of age decline at the onset of puberty. The final section describes interaction of non-demographic variables such as energy and changes in work patterns with demography. Major predictions are that enrollment of elementary school children is likely to continue to decline through mid-1980s, and that the size of the high school population of 1990 will be about 25% smaller than in 1975. It was concluded that although reliable short term predictions can be made for the nation as a whole about the number of children entering the school system, national predictions may not be relevant to state and local planners due to internal migration. (Author/DB)