Kendall, a popular first grader, is continuously in the principal's office. his teacher complains that he does not listen to instructions, he fails to finish his schoolwork, he fidgets and squirms in his seat, he often leaves his seat without permission, and he cannot seem to wait his turn during class activities. whenever the principal calls kendall's mother, she seems baffled by his behavior because kendall does not have any problems at home, at church, shopping, or at daycare. what diagnosis is appropriate?