Hi Indigo, you've certainly summarized thoroughly!
I have definitely known kids that were very advanced in math, very self driven in their math pursuits at home and anywhere they went, and thus generally very recognised for their math gift. If they weren't offered extension and support at school it was never for lack of recognition of how advanced they were.
But I do think, with any area of giftedness, it is incredibly difficult to advocate for a child that doesn't "bring it" themselves for the teacher to see. And I think it's getting harder. At least where I am the attitude of schools towards parents is increasingly dismissive or even antagonistic. Very much an assumption that all parents have blinkered views of their snowflakes and if the school didn't raise the issue the issue doesn't exist.
I didn't reply initially because I really have no tips, I have had no success advocating for my children when they have (deliberately or not) hidden their talents, or had talents which are not valued by the school. I was drawn in by other replies and may have helped things veer off topic...
