NCmom -- there are so many posts over the years that ask this same question. For your individual situation, only you can judge which score seems most accurate. However, this is so common and so many kids score so ridiculously high on the SBV at 4 or 5 years old that I wonder whether the norms for the younger ages are just a bit off. I'm much more impressed with a 140+ score for a kid at 8 than I am for a 150+ score for a kid at 4 or 5. I think even if the norms were perfect, there is much variability still occurring and reshuffling of order that leads to big changes for many kids. IQ scores are not stable for 4 or 5 yo on any test and the SBV seems particularly unstable in that age group. Some kids who score 150 at 5 will also score 150 at 8, but many will not which leads to confusion and frustration for parents.
I like Dottie's idea that time and multiple sources of evidence reveals the most about a kid rather than any one particular score. Achievement testing might help you get a better sense. If the scores are 130-140ish, then the "truth" might be somewhere in the middle or closer to the later score. If the AT scores are wildly PG, then maybe the first test is more accurate. If what you see every day is obviously PG, then maybe the first test is more accurate.
It helps to remember that scores are quite fallible and personality and drive may determine academic needs more than test scores. A kid may test wildly PG and not require dramatic educational changes while another kid may test more moderately and need radical acceleration. If your son needs a different educational environment, then I'd address that need no matter what the test says.
