Chicago ? Children on medicine for attention deficit disorder scored higher on academic tests than their unmedicated peers in the first large, long-term study suggesting this kind of benefit from the widely used drugs.

The nationally representative study involved nearly 600 children with attention deficit hyperactivity disorder followed from kindergarten through fifth grade.

Children’s scores on several standardized math and reading tests taken during those years were examined. Compared with unmedicated kids, average scores for medicated children were almost three points higher in math and more than five points higher in reading. The difference amounts to about three months ahead in reading and two months in math, the researchers said.

Both groups had lower scores on average than a separate group of children without ADHD. The researchers acknowledged that gap but said the benefits for medicated youngsters were still notable.

“We’re not trying to say in this study that medication is the only answer,” but the results suggest benefits that parents, educators and policymakers shouldn’t ignore, said Richard Scheffler, the lead author and professor at the University of California at Berkeley’s School of Public Health.

The researchers agreed that other treatment ADHD children often receive — including behavior therapy and tutoring — can help, but the study didn’t look at those measures.

Most ADHD drug users in the study were on stimulants; the study didn’t identify which ones.

About 4 million U.S. children have been diagnosed with ADHD. About half of them take prescription medication — often powerful stimulants like Ritalin — to control the extreme fidgetiness and impulsive behavior that characterize the condition.

Often, kids with ADHD struggle in class and get lower grades than their classmates. They also have higher dropout rates.

American Academy of Pediatrics guidelines say stimulant drugs are effective but that behavior techniques should also be used.

Teachers often advocate medication because it can calm disruptive behavior. But it’s a contentious issue for many parents, worried about putting their kids on drugs that can have side-effects including decreased appetite, weight loss and insomnia.