The experiences of 150 children in after-school programs were examined in relation to performance in first grade. Three aspects of program experiences (emotional climate, quality of peer interactions, and program curriculum) were associated with the children's concurrent adjustment at school, controlling for family selection factors. Staff positivity in the after-school programs was associated with boys displaying fewer internalizing and externalizing problems, whereas staff negativity was related to boys obtaining poorer grades in reading and math. Program flexibility was associated with boys having better social skills. More frequent negative interactions with peers in the programs were related to more internalizing and externalizing problems, and poorer social skills at school. Boys who attended programs offering a larger number of different activities had more internalizing and externalizing problems, and poorer grades in reading and math. After-school experiences also were related to girls' behaviors, but associations were less apparent for girls than boys.