So whose interests, exactly, does the Clark County School District have in mind as it makes its push for full-day kindergarten?  Apparently, not the students.

The district released a study about a month ago that supposedly proved beyond a doubt that students who attend full-day kindergarten benefit in the long run, thus supporting their claim that full-day kindergarten programs ought to be expanded.

The proof? The study, which examined 1,233 students in the second grade from Sept. 11-22, 2006, found that students who had attended full-day kindergarten performed, on average, 3.1 percentage points better than students who attended half-day kindergarten.

Even better news was that students deemed "at-risk" — classified as such because they qualify for free or reduced lunch due to low family income — saw an improvement of 8 percentage points.

Quite the rosy picture, except that something about those numbers caught the attention of state Sen. Bob Beers, R-Las Vegas, who raised the question of what degree of improvement, if any, was found among those students who were not "at-risk." After all, simple mathematics would suggest the number had to be below 3 percentage points.

According to Beers, district officials were not forthcoming when he first put the question to them directly.

But Beers kept at it, and his persistence paid off.

A March 1 news release from the senator's office reported that, "Finally, after a month of mounting pressure, the district lifted its veil of secrecy this week and confirmed what common sense was telling me … second-graders not "at-risk" who attended full-day kindergarten performed 3 percent worse on standardized tests compared to the half-day kindergarten group."

According to the school district "additional results" report, the mean score for students not receiving federally subsidized lunches declined from 54.76 to 51.72, when they moved from half-day to full-day kindergarten.

This finding is not just a statistical peculiarity. It basically quashes the entire rationalization behind the full-day kindergarten movement.

According to nevadareportcard.com, Nevada's federally mandated Web site for tracking educational performance, 45.6 percent of Clark County students qualify for free or reduced lunch, thus placing them in the "at-risk" category. This means that the other 54.4 percent of students are not part of the "at-risk" group.

Since those who were not "'at-risk" saw a decrease in performance by 3 percentage points, and those students make up a majority of Clark County School District students, then what the study is telling us is that a majority of students belong to the group that is harmed, rather than helped, by full-day kindergarten.

We ask again: Whose interests does the district have in mind?

What Beers uncovered is consistent with what we at the Nevada Policy Research Institute have seen in other studies indicating negative consequences of an increased level of early education.

One study — titled "How much is too much?" — was published a little over a year ago by a joint research team from the University of California, Berkeley and Stanford University. Taking national data from the federal government's National Center for Education Statistics, researchers found that preschool hinders social development and fosters poor social behavior. This was the case for middle-class kids especially.

Another study released in Canada around the same time, in which the C.D. Howe Institute for public policy looked at results from Quebec's universal preschool program, found that "the increased use of child care was associated with a decrease in [those children's] well-being relative to other children."

And academically, studies consistently have found that students who are not considered to be "at-risk" do not benefit from extended preschool programs, and that the benefits to those who are "at-risk" are short-lived.

That the Clark County study reveals similar findings is no surprise. What's troubling is the lengths district officials apparently went to in order to keep those findings from the public. Even worse is the fact that they touted the study as evidence in support of ramming full-day kindergarten down our throats — when the study itself indicated that most students run the risk of being harmed by such a move.

Troubling, but perhaps not surprising, either.

As often with the public education bureaucracy, the announced goals turn out to have less to do with students' well-being than with a mindless thirst for ever greater power and money.

Clearly, in Clark County the institutional imperatives of a huge monolithic bureaucracy are in the saddle.

Against that, the likely harm to most Clark County school kids apparently counts for nothing.

Andy Matthews is communications director for the Nevada Policy Research Institute. This op-ed first appeared in the March 11 Las Vegas Review-Journal.