Wow. That is a hard decision. I'm pretty new to all this, too, but I would like to ask some questions. What did your son think of first grade? You said it was a bad year for getting any accelerated work, but did he enjoy going to first grade? Did he have friends and enjoy it socially? We did a mid-year grade skip this year from second to third and the decision was easier because he was miserable in second grade socially (as well as being bored). Part of the Iowa Acceleration Scale is asking the child what he or she wants to do. I was just curious what your son's decision would be.
The private school sounds like they are willing to work with a gifted kid and let him find where he is comfortable academically (and presumably socially). It sounds a bit more flexible. Have you tried going over the head of your public school principle? We just had a meeting with our school district's curriculum director and found her to be much more understanding of HG+ kids and their needs. Our public school gave us a single grade skip and pull-out classes (which are less than desirable!), but never really seems to "get" our son or his needs. The curriculum director immediately began speaking about asynchronous development in highly gifted kids and made suggestions about additional subject acceleration in science and compacting in math. I don't think we would have gotten that without going up the food chain a bit. You might find that if other schools in your district have a history of accelerating gifted kids, then you can use that as a setting a precedent (even if it is not in your actual school).
I hope some of this helps. If it is any comfort to you, my son did much, much better after a one year grade skip in the middle of the year. He will now graduate from high school at age 16, provided there are no additional whole grade skips. The problem is that he learns so quickly that he mastered all of the material in third grade before the year was out. <sigh> Unfortunately, there are no easy answers when school groups kids based on age and not ability.
Each kid is different and you kind of have to listen to your gut instincts on what you think is best. You know your son better than anyone else, and you are the best person to decide where he should be. Trust yourself.
