KJP-- I don't have any words of help but my son similarly dropped from 90th percentile on WPPSI (at 4) to 16th on WISC (at 6)and now has a 61pt spread. I find myself wishing we could clinically compare these kids we have with such similar issues and figure out all the "whats" and "whys".
My completely unresearched theory is that the expectations for processing are much higher with age.... agemates are making large strides in growth during those years that our children's brains were not able to make.
