What IQ test were your other two children tested on? Although they are all supposed to correlate relatively well, my younger dd tested on two occassions as follows:

WISC-IV: 148
WISC-IV: 127
SB-5: 119

I don't know what to make of my kiddo's erraticness, but she certianly did "better" on the WISC-IV both times and I'm not sure that you can compare scores across the board btwn those two tests.