2. Ceiling effects might be a factor for GT 5 year olds taking the WPPSI, not the WISC. 5 year olds cannot take the WISC (the lowest age is six).
In fact, if it fits into your budget, and you think your child will tolerate it, you have the option of a WPPSI-IV now, and a WISC-V in a year. In both cases, there is a significant likelihood of unstable results, but as long as you view them only as data about present levels (not necessarily rigorously predictive), they can still have value.
If you are viewing testing as a possible component of access to certain kinds of gifted or private programming, it may helpful to survey the kinds of testing that are accepted by those programs, prior to testing. Since you cannot retest with the same instrument within two years, that is also a consideration. (You may obtain more stable, "better" results nearer the deadline for score submission, as your child will be older, and thus more likely to demonstrate the full range of his skills in an on-demand testing situation.)
Yes, sorry about the typo! I of course meant ceiling effects on the WPPSI. The only gifted program that we may apply for accepts both the WPPSI and the WISC. I don't know at this time whether we will apply, but part of my thinking is that testing early would give us all of next year to start a conversation with the school and understand what we'd be getting into. I don't think they'll take us seriously until we have test results, so waiting for the WISC next March might be rushed.
Can anyone shed light on how significant the ceiling factors are? E.g., at what level would a child typically be significantly impacted - 98%? 99? 99.9? I know that I'm oversimplifying, but I'm just trying to get a handle on whether this is a realistic concern or not.
