As part of DD's special ed eval they actually ASKED if they could use the outside WISC IV scores that we have, so that they don't have to spend the time/money to test her themselves. Of course, it's different if it's an assessment for advanced abilities since in most places that's not mandated. But they also accepted her WISC scores for the gifted program, for the same reason. It's cheaper/easier for them. They do, however, have a list of psychologists that they will accept scores from, meaning that our outside results in terms of our other child (from a major university) are probably useless.
