ADD was not a recognised conditon when I was in school. Instead, the counsellors concluded that I was a 99.999 percentile genius, and my teachers were f*****g boring me! Not that it helped - they still didn't have a clue how to handle me. I'd say that the 10% at either end of the IQ scale are beyond the system's ability to cope, leaving 80% that are merely poorly served! :p