From the Wall Street Journal….

If anything, preschool may do lasting damage to many children. A 2005 analysis by researchers at Stanford University and the University of California, Berkeley, found that kindergartners with 15 or more hours of preschool every week were less motivated and more aggressive in class. Likewise, Canada’s C.D. Howe Institute found a higher incidence of anxiety, hyperactivity and poor social skills among kids in Quebec after universal preschool.