The parents of a 14-year-old female high school freshman bring her to the PMHNP for an evaluation. They believe she should be doing better in high school due to her "gifted" status. They state that she has a formal IQ score of 125 and that her grades were mostly As through 8th grade. Now, she hands in her papers late and her grades are dropping to mostly Bs and Cs. During her psychiatric evaluation, the girl reports that high school is different from elementary school and junior high, because now she has to write papers. She says she often turns them in late due to procrastination and forgetfulness. She reports a long history of inability to sustain attention while in class or doing homework, failure to pay attention to details or finish chores or tasks, significant difficulties with time management, planning and organization. She is forgetful, often loses things, and is easily distracted. She has no history of restlessness or impulsivity, and she is popular with her peers. What is the most likely diagnosis?