This report reviews recent research on the effects of changes in school environments on economically disadvantaged, minority group students, discusses methodological problems encountered in such research, and describes a longitudinal study designed to determine how pupil relocation policies might be used to improve academic achievement of black students. It was found that: (1) increases in classroom mean achievement levels have a positive impact on black students' academic growth patterns; (2) students originating in predominantly black sending classrooms benefit academically from moves into majority white classrooms; (3) the optimal type of move for a black student originating in a predominantly black classroom is one in which the receiving classroom is between fifty and ninety-five percent black and reflects a higher academic performance level than the sending classroom; (4) relatively high achieving students experience greater achievement gains in their receiving schools than in their sending schools, whereas low achievers tend to show academic losses in their receiving schools; and (5) changes in pupil/classroom ratios and level of teahcer education and experience are not strongly related to academic growth rate of black students. Limitations of the current research are discussed and implications for pupil assignment strategies are outlined. (Author/JCD)