Hi and welcome! You have found the perfect place to share your frustrations and get support. This is a great bunch of people, many of whom have been in your exact position.
First, let me say that from your post it sounds like you know what is right for your son. You know your son better than anyone, including principals, teachers, neighbors, friends, even family. Don't let them make you doubt what you know to be true.
And be reassured that many of us here have had very successful experiences with our children getting early-K entrance, skipping K, subject accelerating, and grade skipping. We've personally done all of these and my kids are much better for it -- academically and socially. Our experiences at our school, for instance, were the first time they ever happened in our district, and with the success that they've seen with my DD particularly, they've now opened their minds a bit and have allowed other children to similarly be placed appropriately.
It's hard being the rabble-rouser, the innovator, the "pushy-parent." Especially because many of us here tend to be introverts. And you will always meet people who throw out their unsolicited opinions about the evils of grade advancement or even, God forbid, letting your boy go to school young-for-grade. You will have people not so much criticize your decision outright but more just make blanket statements which do not apply to you. Some relationships with friends and family will suffer.
You can try to convince these people they are wrong. You can say that the decision is right for your child. You can tell them about all the research. You can make a smart-alek comment. You can gloss over the intelligence of your child. You can say that your child should have been skipped three grades but you settled for just the one. You can moan about it later to your spouse. But in the end, you just have to do what you know is right and ignore everyone else.
Now, as for getting the schools to at least try early entrance, refer them to all of the research proving the success for well-screened kids (particularly A Nation Deceived) and have the school, if they need to, look into the Iowa Acceleration Scale which helps them make an objective decision.
And keep in mind, too, that schools have a lot of parents coming to them insisting that their children are brilliant so they are naturally skeptical. If you can prove to them that your child really is here at the tail end of the bell curve, that will go a long way. Good luck and know that you're not alone!
