A lack of focus, not hyperactivity, is the main reason students with attention-deficient hyperactivity disorder don\'t finish high school, Canadian experts say. University of Montreal researchers looked at data collected from the parents and teachers of 2,000 children during a period of almost 20 years. Attention problems were evaluated by teachers who looked for behavior such as an inability to concentrate, absentmindedness, or a tendency to give up or be easily distracted. Hyperactivity was identified by behavior such as restlessness, running around, squirming and being fidgety, the researchers said. The study, scheduled to be published in the American Journal of Psychiatry in November, found 29 percent of children with attention problems finished high school compared with 89 percent of children who did not manifest inattention problems. Forty percent of the students with hyperactivity completed high school compared to the 77 percent students who did not demonstrate this behavior. After correcting the data for other influencing factors, such as socioeconomic status and health issues that are correlated with ADHD, inattention still made a highly significant contribution which was not the case for hyperactivity. \"In the school system, children who have attention difficulties are often forgotten because, unlike hyperactive kids, they don\'t disturb the class,\" Dr. Sylvana Cote, the study leader, said in a statement. \"However, we know that we can train children to pay attention through appropriate activities, and that can help encourage success at school.\"