Participants in this study are randomly assigned to OST, CM, or Wait-List (WL). Participants in the OST and CM groups attend 20 1-hour sessions over 10 weeks. OST trains children to use a variety of techniques for improving their organizational skills. Both children and their parents attend every OST session. CM does not involve skills training. Rather, CM trains parents and teachers to identify desired "end" behaviors and to increase the frequency of these behaviors through the use of a structured reward system. Both children and their parents attend every CM session, but the children's participation will be minimal. Participants assigned to the waitlist condition will have the opportunity to receive their choice of either OST or CM once they have completed the study. All participants attend follow-up visits 1 month post-treatment. Participants assigned to OST and CM attend follow-up visits after 1 and 4 months into their next school grade. School performance, feelings about school, ADHD symptoms, organizational skills, family environment, medication or services received, and use of treatment strategies will be assessed at each follow-up visit.