Awww 'Neato, having 2 coming home from school miserable sounds really terrible!
My DS7 sounds like he's in a similar spot as your DD7. "All the work I do at school, I already know". And he is in the class of 26 that is laden with discipinary issues. And it was right after the holidays last year where he started complaining heavily about kindergarten.
"The dumbest one in class" phenomena is interesting. I distictly remember feeling that way as a child, and DS comes out with that every once in a while. I wonder if it has more to do with knowing intuitively that you're different from almost everyone you come in contact with?
I hope DD7's pull out gets back in place on schedule, and the child psychologist will back you up for a grade skip! It sounds like a rough road! Definitely keep us posted.