Wow -- I find it amazing that they'd skip him, not not identify him as gifted! Very odd.
I don't think "not demonstrating what he knows" is a nice way of saying he's not gifted. Is it possible they know he *is*, but don't want to provide services beyond the grade skip? He hasn't been tested yet, has he? Do you think he'd cooperate?
Have you sought more differentiation -- and would he do it? Is he enjoying school?
From what I remember, you're afterschooling informally. How's he doing there -- does he still have that "spark"?
I feel for your ds! It's an awkward spot, adjusting to a grade skip that's probably inadequate anyway. Yikes!