I also meant to add, that I don't think it is unusual for kids who used to be "into" learning all the time at ages 4, 5, and 6 to become less enthusiastic as they get older. My DS8 sometimes is just tired when he gets home from school and just wants to zone out - he may only have energy to focus on the things that he is most interested in . I don't blame him one bit - I feel the same way after work. I don't view this as a sign that he is turned off from learning as much as a sign that I wish I could HS him, just because so much of his time at Public School is sucked up in non-productive ways (and our PS has been working pretty well with us to keep him challenged).
