Hi and welcome!
We just applied this month!
My ds5 took the WPPSI and came back with a PIQ of 144 and a FSIQ of 148. Like you, though, we hit ceilings with a 19, two 18s and a 17. And he got a straight 10 in coding (particularly variable in gifted kids), which has a considerable effect on the overall score. So we're hopeful that they examine the full score report, which I've heard they do. We also had WIAT-II achievement testing done. which allowed us to apply using the scores method: Ds qualified in both math and language composite (with a 160 on word reading). Fingers crossed!
I'd go ahead and get the achievement testing done. It really has been helpful when advocating with the school, and it gives me a better idea of what to be doing with him!
One note of caution/advice: My ds is a number whiz too -- but he does almost all of it verbally. Because we never spent time teaching him many of the written conventions, he doesn't do as well on standardized tests. He perfectly understands and uses percentages, fractions, etc., but he can't always apply this knowledge to the test. You may want to spend some time with him before getting achievement testing done, to make sure he understands all the written symbols. We just figured out that ds didn't know what a division sign looked like! Of course, your ds may know this stuff, but we were/are like you -- no time for hothousing here!
Which meant that ds could do a *lot* of math, but not express it on paper.
