Here’s a pop quiz about your child’s education: true or false—reducing class size boosts student achievement.

That statement is true. But, says a team of experts in this month’s Scientific American, programs to reduce class size can do more harm than good if policymakers don’t do their homework.

Get out your notebooks for this ScienCentral News video report.

Does class size matter?

Programs to reduce class size are increasingly embraced by federal, state and local governments alike. Even as billions of tax dollars are channeled into these efforts, experts disagree about whether class size really matters. The National Education Association enthusiastically supports class size reduction, while the Heritage Foundation argues that the evidence is lacking.

This month’s Scientific American does the homework for us. A team of four independent scientists led by Ronald G. Ehrenberg, director of Cornell University’s Higher Education Research Institute, was asked by the journal "Psychological Science in the Public Interest" to examine the issue. Their review of the research was published in May.

The team examined hundreds of studies on the effects of class size on academic achievement. All are independent scientists who had not taken any position on this issue before, according to Ehrenberg. In their summary for Scientific American, the scientists also consider "the great cost involved in reducing class size," says Ehrenberg, "And we talk about other possible problems that are involved, including the fact that you can only reduce class sizes if you have space to put the students. And in many districts this is going to require more buildings."

Their conclusion: Smaller classes do indeed boost academic performance, but "in a very specific way: It’s important for students to be exposed to a small class early on in their educational career," says Ehrenberg. "And there appears to be long-lasting gains from doing so." But, he adds, "there do not seem to be any additional advantages from persistently keeping children in smaller classes."

In fact, the one experimental study they judged to be scientifically valid, Tennessee’s Student-Teacher Achievement Ratio (STAR) project, persuaded Ehrenberg that ensuring children get one year of small classes (about 15 students) in the early grades (K through 3) can give them an advantage that lasts through high school.

Ehrenberg urges state and local policymakers to weigh the costs and benefits before implementing larger-scale class size reduction programs, and he warns that they will not solve all of America’s educational woes. "All the pressure for reducing class sizes is also coming at a time that many of the nation’s teachers are retiring, and we’re having great difficulty finding people to replace them," says Ehrenberg. "If we’re serious about wanting to improve American education, we have to make teaching a profession that the public values and pay substantially higher salaries and have better working conditions to attract new people into the profession.

"I think the real dilemma that our society faces, or will face—and we won’t face this until after we get over the current financial and social crisis that we’re involved in—is: How important is education to us as a social priority?"