I am in a huge district (well over 100,000) that employs quite a few attorneys so tends to be on top of relevant legislation.
As you say you have dealt with them before, I am sure you are aware of this, but being a public sector lawyer myself (not in the US, but these things are the same the world over), let me remind you that they will be expected to be picky about which legislation the are on top on. So it's always a good idea to be on top of things yourself...as you appear to be.
About your question: again, not in the US, but we will be in your situation next year, with DS1 being in fourth grade in elementary school, and fifth grade will be in the middle school next door. SSA in math has sort of worked, a bit, for this last year, but I cannot think of any way to make it work next year, as scheduling between elementary schools and middle schools is just too different, there is no way we'd be permitted to let him just walk there on his own and hang out in fifth grade classes there, and tracking rules being such efficient gatekeepers. We looked at the matter from all sides and have decided it's either coast for another year in fourth, with all the after school enrichment we can do, or a full on grade skip into fifth grade in the gifted program across the city right away. Because he has already been accelerated once (early entrance) and the school was sceptical, and most importantly because he was not ready to leave his current class, we decided against.
He is complaining again, about boredom, the repetition, the pace (we're not off for summer yet)...I now remind him, gently, that it was his choice and why, not in a I told you so way, but in a you have agency and have used it way. Fourth grade may be even worse, or it may be better, as supposedly standards are to be raised to prepare kids for middle school and facilitate tracking choices (they work the kids hard, and those who are left behind will not make the GPA for higher tracks, it's cruel but effective as a sorting mechanism). One of the reasons we feel we can risk it is that we do have a good option with the gifted program starting in fifth, we hear that even PG kids are happy with the program, so it's all a matter of biding our time.
Has your child been accelerated before, ie a full grade skip, making him very young in his grade already? Will you have other acceleration options, such as accelerated classes for kids who test into them, come sixth grade and up? Is he truly so lopsided in his profile that he is challenged already in his current grade in the subjects you haven't sought SSA for? Because if not, you may want to look at the full grade skip again.
