I have moved my kids a lot and thus dealt with a few different school districts. I have had to go to bat for my kids and I have never regretted it.
First, I’d echo others with make sure what your son really wants and not just based on his imagined future. Not doing an advanced track might shut him out of the most elite schools but doesn’t close all doors, not by a long shot.
Does he want to work harder and be more organized?
Does he do better in a class with more pressure to excel and brighter students or does he do better when he can shine high above his classmates?
In short, are you convinced he really wants and can handle an accelerated track?
If he really wants it and is ready to work for it my experience is that you have to be patient, persistent, and polite. Don’t take no for an answer. Assure teachers and the administration that you are fine with your child receiving low grades if that is what he earns (and you do have to mean this thus the questions above). Schedule meeting after meeting. Go slowly up the chain and show respect to everyone at every step of the way. Don’t burn your bridges.