[Editor: This is a synthesis of research dealing with effect of general formal education on small children. While this is not directly associated with abstinence education, it points to the damage that can be done by teaching inappropriate information to children too early. The same would hold true for teaching children in the latent period about sexual matters…]
Excerpt p. 4-5 (emphasis added):
A significant body of research shows that formal early education can be detrimental to mainstream children. David Elkind, professor of child development at Tufts University and author of numerous books on cognitive and social development in children and adolescents, explains:
“The image of child competence introduced in the 1960s was intended to remedy some of the social inequalities visited upon low-income children. But the publicity given the arguments of child competence was read and heard by educators and middleclass parents as well . . . For this reason it was uncritically appropriated for middle-class children by parents and educators. While the image of childhood competence has served a useful function for low-income children and children with special needs, it has become the rationale for the miseducation of middle-class children…” 
Elkind explains that children who receive academic instruction too early — generally before age six or seven — are often put at risk for no apparent gain. By attempting to teach the wrong things at the wrong time, early instruction can permanently damage a child’s self esteem, reduce a child’s natural eagerness to learn, and block a child’s natural gifts and talents. He concludes:
“There is no evidence that such early instruction has lasting benefits, and considerable evidence that it can do lasting harmIf we do not wake up to the potential danger of these harmful practices, we may do serious damage to a large segment of the next generation…” 
The notable absence of benefits for mainstream children coupled with evidence that early education programs can be detrimental to their development should be of critical concern in light of the fact that policymakers seek preschool and full-day kindergarten for all children, not just the small percentage classified as being at risk for school failure. 
Excerpt p. 9 (emphasis added):
Therefore, the reasonable conclusion to draw from the Reading First analysis is that, while we cannot be confident in the advantages of full-day kindergarten, we can be sure that, if those advantages exist, they also fade quickly. This finding would be consistent with the highest quality research conducted to date on kindergarten programs.
Excerpt p. 9 (emphasis added):
The ECLS-K research shows the same pattern documented by hundreds of early education studies: children in full day kindergarten are afforded a modest academic edge over children in half-day kindergarten when measured at the end of the kindergarten year. However, that initial edge completely disappears by third grade.
At the end of the kindergarten year, the researchers find there is “little meaningful difference” on reading and math test scores between all-day and part-day kindergartners. . . .
Excerpt p. 18 (emphasis added):
The Department of Health and Human Services (HHS) has maintained that research proves Head Start’s effectiveness. In a letter to the GAO, June Gibbs Brown, then inspector general of HHS, wrote, “There is clear evidence of the positive impacts of Head Start services.”  For supporting evidence, HHS cited findings from a comprehensive synthesis of Head Start impact studies conducted under HHS auspices in 1985.  The study showed that Head Start could have an immediate positive impact on cognitive measures, social behavior, and child health. However, HHS neglected to mention the rest of the findings — namely that the short-term impact of Head Start diminished once the children entered school.
The synthesis concludes:
“In the long run, cognitive and socioemotional test scores of former Head Start students do not remain superior to those of disadvantaged children who did not attend Head Start.” 
On the three cognitive measures tested (IQ scores, school readiness, and achievement test scores), the report found:
“Once the children enter school there is little difference between the scores of Head Start and control children . . . Findings for the individual cognitive measures — intelligence, readiness and achievement — reflect the same trends as the global measure . . . By the end of the second year there are no educationally meaningful differences on any of the measures.” 
Findings on children’s social behavior, achievement motivation, and self-esteem were similar:
“On social behavior, former Head Start enrollees . . . drop to the level of comparison children by the end of the third year. On achievement motivation and self-esteem, Head Start children drop below non- Head Starters a year after Head Start, then score about the same as comparison children for the next two years.” 
[Document: “Assessing Proposals for Preschool and Kindergarten — Essential Information for Parents, Taxpayers, and Policymakers,” Darcy Olsen, Goldwater Institute Policy Report No. 201, February 8, 2005. <http://www.sjlpp.org/documents/proposals.pdf>]