As a Gifted Youth Coordinator for my local Mensa group, I know that Mensa does not do any testing for anyone under age 14 and the testing that Mensa administers for individuals ages 14+ is solely for admission to Mensa. It correlates with IQ, but it is not an IQ test so it likely would not be usable for anything else like admission to a gifted program or the Davidson Academy.
If the testing your ds had was for Mensa admission, it must have been something done privately and that might be something that would work for a DYS application if the score was in the 99.9th percentile+. The criteria posted by Peter above is probably the best place to start to see if he has qualifying scores on the types of tests that DYS takes.
