Greg Toppo of USA Today directed me to Emily Bazelon's thoughtful analysis on Slate last week of the study of child care. (I refuse to use the term "day" care. It's children being cared for, not "days.") She spoke with one of the authors who pointed out that in the sample of children studied there was a correlation between amount of time children spent in child care prior to age four and a half, the quality of the care received by those children, and the very, very slight increase in problem behaviors observed in the fifth grade. Those who were in child care for more years received, on average, lower quality care and had more problems. Bazelon astutely reminds us that infant care is not only the most difficult to do well and the most expensive to offer but also that infants benefit least from the group interactions that characterize good child care for slightly older children. (All of this reintroduces the question that many private child care centers have about publicly funded preschool: the older kids in such centers subsidize the infants. When the older kids are siphoned off by free programs, that makes the economics of private child care for infants even more tricky.) Here's a quote:

It's useless to rail at the press for leading with the bad news and for ignoring the researchers' caveats that no cause-and-effect conclusions can be drawn from their data. Still, coverage like this feels designed to twit working parents. And it turns out that in the case of day care, the headlines and the stories really were alarmist—even wrong.