In a report published by The Heritage Foundation, Jenet Jacob Erickson, Ph.D., writes:
The evidence of negative social-behavioral effects associated with outcomes of non-maternal care ... raises questions as to the benefits associated with currently proposed universal pre-K educational plans. Evidence of cognitive benefits associated with high-quality pre-K educational plans has already been questioned, and this review presents a strong case for potentially negative social-emotional and behavioral outcomes associated with early child care.
Further, the negative social-emotional and behavioral effects did not seem to be ameliorated sufficiently by higher-quality child care. An informed discussion of public policy around universal pre-K plans should include consideration of this evidence for potentially negative social emotional outcomes.
Erickson also says "tax policy should relieve the pressure on families rearing infants and young children," an idea I wholeheartedly endorse.