Thanks, Grinity--that is very useful info about the tests. It seems like WPPSI gives sort of funky results. I would be more in favor of testing if he could take the WISC.

I need to find out more about how having his sister there would influence his chances of getting in even if he did not already attend. It is not a lottery--after you have the IQ score, they look at grades, attendance, and I think a few other things, so they have some leeway.