ooooh and this is from the APA
http://www.apa.org/releases/childcare.html
and this is from just some dude on the internet, so who knows how credible it is:
http://biologyofkundalini.com/article.php?story=Zeroto3Years
Actually, it’s fairly accurate. Too much depth for this discussion, but a positive relationship between a mother and child helps with the development of the brain more than anybody wants to really admit. They want their big homes, their cars, their separate lives. They don’t want to think that their more lavish lifestyle may be detrimental to their kids. They don’t want to have to make sacrifices. People want to feel correct, so it won’t surprise me if you denounce these articles. Actually, I’ll more than expect it. 
But I know in my heart of hearts that it is very important. It’s not some huge conspiracy against women in the workforce.
Have you seen mothers of children who can’t behave well? They’re horrible. Seldom do they hold their childs hand when walking in a parking lot or store–they let the child walk behind and hope they get run over or kidnapped. There is zero attatchment. The best thing for a child is quantity AND quality time with the mother. Since not too many people understand this, the quality of students isn’t going to improve. The education system isn’t going to be much help, and the students who had proper parenting all along and not just some of the time are going to do better.