Does daycare affect a child’s behavior and development? It all depends on the quality of care.

Asking how daycare affects a child’s behavior and development is a lot like asking how parenting affects a child’s behavior and development. The short answer is, daycare has a variety of measurable effects, many of them positive and some of them negative. And they hinge on the quality of the care, the type of care, and the amount of time spent in it, pretty much as with parenting.

Researchers now know that the nature of daycare arrangements (more than ten hours a week spent in the care of someone other than the mother) has a long reach. The type and quality of care can influence many aspects of development—including memory, language development, school readiness, math and reading achievement, the nature of relationships with parents and teachers, social skills, work habits, and behavioral adjustment—at least through grade school. That’s important because in many domains, patterns established by the third grade tend to become highly stable and enduring.

The single best source of information about the effects of childcare is the still-ongoing study begun by the National Institute of Child Health and Human Development in the early 1990s. In 1991, the study enrolled 1,364 children at birth in ten locations around the U.S. and carefully observed and monitored them periodically in whatever care situations their family chose—center-based daycare, daycare in a home, at-home care (including maternal care and nanny care), grandparent care, father care. The study has continued to monitor them through grade school and beyond.

Recently, a new wave of results was released and made news because they confirmed and bolstered the validity of an earlier finding that daycare is associated with some negative effects on child behavior. The study found that the more time a child spent in center-based daycare before kindergarten the more likely their sixth grade teacher was to report that the child “gets in many fights,” is “disobedient at school,” and “argues a lot.”

The authors stress that their study is correlational, and thus it cannot say for sure what is the cause of the aggression and disobedience. They also emphasize that the size of the effect is small. However, because the quality of childcare in the community varies much more than it does in the study, it could actually be understating the effect of center-based daycare on problem behavior. But even a modest effect on behavior would have a big impact in classrooms around the country. The researchers emphasize that many millions of children are in daycare, and for 60 percent of them, the care-giving is neither sensitive nor responsive to their needs.

The study authors suggest that the correlation between center care and problem behaviors could be due to the fact that center-based child-care providers often lack the training, as well as the time, to address behavior problems. For example, center-based child-care providers may not be able to provide sufficient adult attention or guidance to address problems that may emerge when groups of young children are together, such as how to resolve conflicts over toys or activities.