Fastcar - I think everyone here would certainly agree that there are levels of giftedness. And your school psych's problem might be that your son's FSIQ puts him right on the cusp of moderately and highly gifted (depending on where you set your yardstick), so maybe she's hoping to get a slightly higher number for a more definitive level? Alternately she just doesn't know what to make of the SB5 and wants a test she personally is comfortable with.
How did you choose the tester you took your son too? Were they a gifted specialist? If so, then chances are they will have coaxed your son's best performance from him, where as it is a common experience for parents to be less than pleased with school testing (though it can of course be fine).
Also, at 5yrs 8mths and definitely gifted you will run into problems with ceilings on the WPPSI. My DD did the WPPSI at 4yrs9mths and had problems with this.
In terms of figuring out your DS's LOG (level of giftedness) and comparing the SB5 and Wechsler tests, there seem to be a few different ideas around. According to Davidson DYS entry requirements SB5 and the WISC are of equal value number wise (a score of 145 will qualify) while the WPPSI, which is what your DS could sit at his current age, requires a score of 150 to qualify. Hoagies on the other hand lists lower SB5 scores as being equivalent to the WISC or WPPSI. You can see their chart here:
http://www.hoagiesgifted.org/highly_profoundly.htmGoing by Hoagies your son would fall into the exceptionally gifted range. If you take the Davidson approach that SB and Wechsler scores are more equivalent then he would be more in the HG range. Only time will really tell though. A test is one day in time, he's clearly gifted, just how that will play out will take time.
