This is why most GT program starts at third or fourth grade. I seem to recall for all the kids tested gifted at 4 or 5 for K entry, only 30 or 40% will test gifted at 8 or 9, and a lot of truly gifted kids won't test well at a younger age due to maturity issues.

Of course, the higher the number at 4, the less likely the child is going to slow down later. But at the margin, the false positive/negative rates are high.