That's compared to children who don't start stimulant medication until age 11 or 12.
The study in the journal Pediatrics looked at data of nearly 12,000 children from Iceland.
Those taking ADHD medications by fourth grade saw a very small drop in their math score, but the children who didn't begin medication until sixth or seventh grade had a 9 percent drop in their scores.
Experts say the medications do not make children smarter, but that they target symptoms such as focus issues and impulsivity that can affect academic performance.
