An article by the AP, "Study links ADHD medicine with better test scores," reports that kids with ADHD who take medicine have test scores in math that are on average 3 points higher and in English that are over 5 points higher on average than kids with ADHD that are not on medication. Both groups score lower on average than kids without ADHD. It is unclear from the article whether or not the results were based on randomization. Will have to look at the original study.