Had he been in the MG range the results would not have been much different than on the WPPSI.
I'm belaboring a point, so I'll beg your forgiveness right off the bat! Before I go there, though, it sounds like the WPPSI and WJ-III scores are PG anyway so I don't question the SB-LM in your ds' case or, honestly even know if it was necessary to tell you that.
That aside, in regard to the statement that MG scores would not have come out much different on the LM, which I assume the GDC told you, the only data available online about WPPSI and WISC scores vs SB-LM scores for kids who've been tested on both does show some significant score changes for both kids with HG-PG scores on the Weschler scales and kids with MG or below scores on the Weschler scales.
It is on Hoagie's and has kids with scores in the 125-130 range who wound up with 145-170 scores on the LM as well as one with a 112 FSIQ on the WPPSI who then got a 178 on the LM. All of the kids with scores in the bright-MG range saw significant increases on the LM.
Carolyn's notes say that,
Average score change from WPPSI / WISC to Stanford Binet form L-M (SB L-M) for this sample is 27.4+. The range of score changes from the WPPSI / WISC to the SB L-M is -12 to 76 points increase in WPPSI / WISC full scale to SB L-M Pinneau correction or deviation formula score. Only 4 of the 63 children's scores decreased when subsequently tested using the SB L-M; one child's score showed no change.
Off soap box... sorry I'm just not a big fan at all of using the LM anymore although I know that the GDC disagrees. Your little guy sounds like a great candidate for DYS, though, and like he'll be an interesting one to watch grow up with his passion for learning.
