This dissertation investigated, under conditions of court-ordered desegregation accomplished by "forced" busing, the assumption that desegregation brings achievement gains for blacks but that it has no negative effects on white achievement. Reading and arithmetic achievement of a sample of 429 upper elementary students (both black and white, male and female) in Jacksonville, Florida was the focus of the investigation. The sample, of low ability, achievement, and estimated family income, appeared representative of the population. Subjects were desegregated by court-ordered busing at the beginning of the fourth grade. Findings indicate that when language is excepted, blacks showed large increases in reading achievement during the first year of desegregation, and whites showed generally stable levels of achievement. However, both black males and whites showed anomalous declines in language. In arithmetic achievement, blacks again showed increases, but whites showed very large declines. Based on the results, it was concluded that the assumption that desegregation brings black achievement gains was confirmed, while the assumption that white achievement is unaffected was not. This study leaves unanswered the question of whether these findings are due to changes in the type of school peers and level of proportion white experienced by each race, or to the general systemic disruption of the first year of desegregation. Also suggested is that a teaching/instructional effect may be the root cause of the observed black gains and white losses. (Author/AM)