With the first two cases, I would say it's above normal behavior, but not to the extent that it could be diagnosed as ADD. Many people daydream off the drop of a hat in many situations, but the fact that you are getting good grades while having trouble concentrating is normal. A friend of mine in high school who was diagnosed with ADHD had trouble concentrating to the point where he couldn't focus on exams and was given permission to have personalized, more private testing areas with more allotted time to complete it. He would also wander off in conversations frequently. If your concentration lapses worsen, then you might consider seeking a second opinion, but as it's not affecting your grades or social situations, I would say it's normal.