It is difficult to reconcile the positive (and large) effects of Early Head Start on 3 year olds with the lack of positive findings in the first year of the first year findings of Head Start impact study. It is possible that the positive effects found are overstated because it does not take the effects of sample design on standard errors.
Something as important (and controversial) as childhood development assessment does not need sampling design effects to further confound the public. It is therefore hard to reconcile the resistance against the Head Start National Reporting system (HSNRS) that tested every child (as much as possible) in Head Start and was not subject to sample design effects with the desire and even need to see positive impacts of Head Start. The resistance stems entirely from the appropriateness of the assessments used in HSNRS.
The challenge for early childhood educators is to come up with a way of assessing impact appropriately. Why should this be so difficult when parents can (and are even encouraged to) use developmental milestones to guide them in seeing if their child is showing adequate progress?
There is a vocal minority who believe that children should NEVER be tested at such an early age (3-5) and it is possible that this is the minority who are driving public policy regardless of any desire to investigate the effectiveness of Head Start. Moreover, they (and others) believe (perhaps correctly) that the research is used to drive funding and not improvement of programs. Less effective (however defined) programs would be defunded rather than shown how to improve. Does politics trump the need to find out if such programs are effective and how these programs can be improved?
Samuel J Meisels and Sally Atkins Burnett, The Head Start National Reporting System: A Critique
John M Love, et. al., The Effectiveness of Early Head Start for 3-Year-Old Children and Their Parents: Lessons for Policy and Programs