Dalton Conley, NYU sociologist, father, and author of Parentology: Everything You Wanted to Know about the Science of Raising Children but Were Too Exhausted to Ask looks at the academic results of day care by professionals versus home care by moms:
My reading of the “mommy wars” literature is that the secret variable that resolves many of the contradictory studies is social class. Namely, rather than it being good or bad per se for a mother to stay home with her young children, the effect seemed to depend on the socioeconomic status of the mother herself. The more time that highly educated mothers were with their kids — as opposed to sending them to day care — the better those children did on cognitive tests. But for less educated mothers, kids did better when they went off to preschool and other structured activities. Hence the big effects of Head Start and other such programs prepping low-income toddlers for K–12 schooling. But also the negative effects in Canada, for example, when universal pre-school was instituted.