LMom, the tutor told me there are 150 children in the course, some as young as four. My DS7 is in second grade. There was no qualifying necessary once he was in epgy. And quite frankly, he was basically refusing to read at all, so I thought he wasn't even at a 3rd grade level. Figured I could read to him, and then he could read and answer the computer questions, as his comprehension is years ahead of his reading. Turns out he's reading at a much higher level, but the tutor did suggest some strategies to get him to start reading chapter books on his own.
I am very surprised DS likes it so much, but I think the big attraction for him is that it already has him a year ahead of his grade. I am very happy with stanford epgy and think I may use them for his next math course instead of cty.