But is strapping a backpack on all 4-year-olds and sending them to preschool good for them? Not according to available evidence....
Why don't preschool gains stick? Possibly because the K-12 system is too dysfunctional to maintain them. More likely, because early education in general is not so crucial to the long-term intellectual growth of children. Finland offers strong evidence for this view. Its kids consistently outperform their global peers in reading, math and science on international assessments even though they don't begin formal education until they are 7. Subsidized preschool is available for parents who opt for it, but only when their kids turn 6.
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.
The only preschool programs that seem to do more good than harm are very intense interventions targeted toward severely disadvantaged kids.
I have no problem targeting "severely disadvantaged kids". That wouldn't be "universal", and neither would it be "mandatory".
Kids with loving and attentive parents -- the vast majority -- might well be better off spending more time at home than away in their formative years. The last thing that public policy should do is spend vast new sums of taxpayer dollars to incentivize a premature separation between toddlers and parents.