I don't think the site itself was done by native English (of any type) speakers and there is some strange syntax in the directions. Plus the directions are vague. When you get to, "Be honestly to click the word you have seen, or studied or known before." does that mean if I've SEEN a word I should check it? There were a few in there I'd seen but to which I couldn't assign a meaning.

I scored well, but I had a college-level vocabulary when I was 9. My school was testing me because I was having problems. Too bad nobody'd figured out ADD back then.