From my limited understanding (DC did some recent testing), those 19s could indicate reaching the ceilings (I believe in some cases, even an 18 can be a ceiling, depending on subtest and age of the child). Did your tester use extended norms? In my experience, extended norms could make a big difference!

Also, I'm going to guess that as is common with MANY gifted kids, your DC's GAI would be even higher than FSIQ, and might be the better measure.

Those look like very high scores!