The following hypotheses were tested in this study: (1) boys and girls have an even start at school entrance, but boys' performance and adjustment decline relative to girls by the end of third grade; (2) boys do not attach themselves to school and school tasks with positive affect as much as girls; and (3) thus, the factors related to achievement at the end of third grade are different for the sexes, as are the relationships of third-grade achievement to kindergarten entrance variables. Data were examined for white boys and girls of a cohort of 300 children tested at their entrance into kindergarten in 1970, and at the end of third grade in 1974. Measurements for the children at both points included tests of cognitive ability, social-emotional variables and achievement, as well as educational advantage level of the home environment. The analyses of the data from this sample indicated that each of the hypotheses was supported to some extent. There were indications of an even start and of decline in some measurements of boys relative to girls in achievement and adjustment during the early school years. For girls, both affective and cognitive measures at the end of third grade were positively correlated with achievement, while for boys only the cognitive measure was so related. However, it was with boys, not girls, that third grade achievement showed many positive correlations with kindergarten entrance variables. (Author/MP)