If your GT/advanced child is 11 to 13, then they should probably take the SAT so that you have meaningful statistics for comparison to other GT/advanced kids. For a GT/advanced child who is 10 and not grade accelerated, then the SAT 8/9 is the assessment of choice. That is the NUMATS practice as SAT and ACT testing are for 6th graders and up.
The problem with the PSAT is that it is not only easier, it is shorter. A huge part of the SAT is the endurance/focus aspect. That is one reason why (at least theoretically) College Board didn't approve of super young kids signing up for the SAT and only working 1/3 of the test - I imagine that the score may be somewhat inflated compared to students who are exhausted from working the whole test. While there is vertical alignment and therefore significant correlation between the PSAT and the SAT, it is probably not valid to compare one kid's PSAT score to another kid's SAT score.
It is more meaningful to see statistics for other GT/advanced kids because the grade level standards are so low. If your kid takes the PSAT, you won't find much meaningful data. The new SAT 8/9 is replacing the Explore, so that will provide meaningful data if your kid is not quite ready for the SAT.
