(From my phone) Ditto on hearing about a "mathy" skew, but our evenly developing DS5 did fine overall. The test has plenty of headroom, no worries there. There are the equivalent to extended norms, can't recall the name right now, but the documentation IIRC says they're only for people above 160 and they seem to be of little value. They won't allow an alternate calculation to boost one over a 145 threshold (in this complete layperson's belief). DS5 hated the test, as he seems to hate all tests. A benefit on the SB5 is the routing questions, used to get to a good starting place for the individual and cut down on test time/stress, although if your kid tests well it will still take significant time. SB5 also has looser time restrictions than WISC. Good luck.
ETA: According to Deborah Ruf
here, the Extended IQ (EXIQ) scoring is available for those with a full scale IQ (FSIQ) above 150. So according to that, EXIQ scoring won't get one over a FSIQ 145 hump based on reaching ceilings on subtests.
