Imagine the FDA was conducting a clinical trial about a medication that nearly one million toddlers use every day. Families have been using the drug since the 1960s, but experts are unsure of its real effects. Congress finally mandated an evaluation in 1998.

But four years after data collection for the clinical trials was completed, the FDA still won’t publish the results. Many suspect that their stonewalling has something to do with powerful pharmaceutical companies that will be embarrassed if the results are disappointing.

American parents would be outraged—protesting outside of the FDA, demanding answers. Investigative journalists would be probing for results and looking for whistleblowers to give the public the facts.

Unfortunately, we have heard no such outrage, or seen no such digging, to date, demanding answers from the Department of Health and Human Services (HHS) about the four-year delay in the final results of the Congressionally-mandated evaluation of the federal Head Start program, which impacts millions of American children.

Launched in 1964, Head Start’s mission has been to improve the school readiness of low-income children through education, health and nutritional services. Head Start is the nation’s largest preschool program, serving an estimated 904,000 children. The federal government spends in excess of $7 billion on Head Start annually, for an average cost of about $7,600 per child served.

The Left champions Head Start as a key component of “war on poverty” efforts, arguing that investments in early childhood education lead to lasting results later in life. President Obama himself trumpeted this talking point in a 2007 speech: “For every $1 we invest in these [early childhood education] programs, we get $10 back in reduced welfare rolls, fewer health care costs, and less crime.”

This sounds like quite a bargain. Given that total federal spending on Head Start exceeds $180 billion over the program’s lifetime, if the president’s theory were true, one would expect other federal welfare and poverty programs to have been rendered largely unnecessary. Some experts warn, however, that government-run preschool programs like Head Start may not be as valuable as its supporters claim. They note that observed benefits from such preschool programs tend to fade over time.

To settle this debate, when reauthorizing the program in 1998, Congress mandated an empirical study to measure whether Head Start really provides lasting benefits. Using a “random assignment” study (considered the gold-standard of empirical research), evaluators tracked 5,000 low-income children eligible for Head Start who were assigned to two groups using a lottery. The lottery winners attended Head Start, while the losers didn’t participate in the program.

Data collection for the first phase of the “National Head Start Impact Study,” began in 2002 and ended in 2006, tracking Head Start participants from ages 3- and 4-years old through first grade. In 2006, the Department of Health and Human Services extended the study to track these students through the end of third grade to determine whether Head Start yields lasting benefits.

In January 2010, after four years of “analysis,” the HHS Department finally released the results on Head Start’s impact on first graders. The study found that, compared to their control group peers, Head Start failed to boost students’ cognitive abilities across 41 measures. Moreover, first grade teachers reported that former Head Start students were actually less prepared in math than the non-Head Start students.

Now, in 2012, we await the final results of the follow-up study on Head Start’s impact on third graders. Data collection for that study was completed in 2008. Why hasn’t this information been released? It’s hard to imagine that it really takes researchers four years to analyze an evaluation of 5,000 youngsters. After all, the United States fought and won in the Pacific and Atlantic fronts of World War II in less time.

 It’s less hard to imagine that HHS bureaucrats may be delaying the study’s release if it undercuts the administration’s efforts to increase spending on preschool programs—and therefore to increase their own budgets and power.

Americans deserve answers: Billions of taxpayer dollars are at stake. Parents deserve answers too so that they can make educated choices about their child’s care. If Congress and the White House really care about improving the life prospects of the low-income families that Head Start is supposed to serve, then they should demand that HHS cease its foot-dragging and make the results of this study known immediately.