I see stuck on stupid here. Could be CNN is too, and this was a 6th grade class. I think the grades and ages should look like this:
8th 12, 13
7th 11, 12
6th 10, 11
5th 9, 10
That means all the characters flunked at least once, if CNN got it right. The 13y/o would have flunked 3 times.
course being CNN and all, it might have been a 7th grade class...