The researchers said the enduring effect of child care quality is consistent with other evidence showing that children's early experiences matter to their language development.
The long-term effect on behavior also may have a logical explanation, the researchers said.
"One possible reason why relations between center care and problem behavior may endure is that primary school teachers lack the training as well as the time to address behavior problems, given their primary focus on academics," the researchers said.
The study appears in the current issue of Child Development. The authors emphasized that the children's behavior was within a normal range and that it would be impossible to go into a classroom, and with no additional information, pick out those who had been in child care.
Still, the differences in behavior do merit more study, particularly on classroom and playground dynamics, the authors said.
"We regard (the behavior) as noteworthy and meaningful because of the large number of children in America who experience extensive and/or low quality child care prior to school entry," they said.
