Just one other thought: Just b/c IQ scores may not be as stable or reliable in a young child, some of the kids who are getting these really high scores will turn out to be HG or PG. HG+ kids are HG+ kids even when they are little kids, so I wouldn't automatically assume that preschool IQ scores are wrong. I'd just take them as a ballpark estimate and see how things develop over time to ascertain if you want to retest later (if the earlier scores seem off in either direction).

Study Strategies for Accelerated Learners