Hyperactivity may be a cause of classroom drama when ADHD patients are young, but a new study suggests that inattention is the biggest hurdle to academic success. University of Montreal researchers collected data on 2,000 children during a 20-year period. They found that 29 percent of kids who had attention problems finished high school, compared with 89 percent of children who didn't have attention problems. And 40 percent of ADHD children whose primary symptom was hyperactivity finished high...