Oh goodness Knute!
I would call the teacher and ask for a meeting face to face 'to figure out why DS doesn't want to go to school.' At the end of the meeting ask 'would you support me to go to the Principle to ask for help in figuring out why DS doesn't want to go to school and what help can be provided.'
Then meet with the Pincip even though others have found it futile - you have to cover your bases. Next step is school board or local paper.
Possible good outcomes might be: Visit 1st grade gifted class on a regular basis, individual IQ and achievement test to look for a 'fuller picuture' of what he needs, GT coordinator creating a pull out group of kindys.
I would visit the gt class and observe if you think it would be a benifit to him, and then place him where you're mom-gut tells you he has the best chance to be happy.
Hugs
Grinity