Greetings from another Canadian imposter
My DS8 did the CCAT a while ago but the school hasn't shared the results as of yet. When they do I can let you know how they compare to his WISC results. It is meant to test ability as opposed to achievement which generally depends a lot more on environment and exposure. Of course despite their best efforts to focus on ability I'm sure there are ways that knowledge comes into it which is why things like testing ESL kids can be a challenge. I don't think any amount of enriched environment is going to make an average (or even high average) kid test above 99th%ile.
From what I've read and heard the CCAT is a decent predictor. The main criticism I've heard is that it misses kids more than it over identifies (2e kids for example). My DS is 2e so I will be very interested to compare his results.
Finally, onto the imposter stuff. I had a similar reaction a couple years ago with DS's first WISC scores but eventually came around. Yesterday we received his new even higher WISC scores and I'm going through a second round of shock so I empathize.
One thing that helped me put it in perspective was thinking about it as 1/X where X is how many people have a particular IQ or higher. Looking at around 90th%ile (120 IQ on this chart) you're looking at 1/11. Moving up a bit then look at 135 (99%ile) and it is 1/102. And so on. Thinking about my graduating class of around 500 kids and it seemed like less of a shock (at least for me, of course YMMV).
http://www.iqcomparisonsite.com/iqtable.aspxAs for the evening out thing, this has certainly not been the case for us. The older DS gets the more obvious it is becoming. Of course our DS was/is very asynchronous and in many ways was behind in school rather than ahead until reading finally clicked for him.
