I found this article last week and it seemed to make sense:
http://abcnews.go.com/GMA/AmericanFa...2877896&page=1

DH's son was constantly told how smart he was and as time went on he did less and less effort and of course the school was always to blame for not being able to keep him from getting "bored". Well he eventually bored himself out of decent grades altogether and never wanted to do anything but play computer games til 3am. He almost flunked out of college several times but is improving now slightly (in his 5th year!).
I see this so much these days...