My perspective:
I'm a physical scientist by avocation and training, as is my spouse, and we've both been post-secondary educators in those disciplines as well...
plus our DD is a high school student at the moment, and has definitely got substantial math and science ability/interest.
Her acceleration in math seems to be about right, and this is probably an area where she is more like EG rather than purely PG. That is, she has to work at anything beyond Geometry, though we still find areas of intuitive understanding of concepts and she certainly learns much more rapidly than other classmates.
With that said, I think that the EPGY model has a lot to recommend it, here.
DD could (maybe 'should') have, IMO, taken AP Physics B this past year, while she was taking Algebra II. I would probably hold off on AP Physics until after a student has completed Geometry, simply because so many courses up to that point either skim or don't cover the geometry concepts presented in the texts at all. That material is useful in Physics, even in algebra-based physics, IMO.
I don't necessarily think that taking AP physics this early is the right move for all mathematically gifted students, some of whom may well prefer as less practical/applied approach to things.
For mathy kids with a more theoretical bent, I'd probably enrich mathematics with statistics, modeling, or economics instead after Algebra I, Geometry/Algebra II.
My daughter is not one of the 'theoretical' kind; she did not enjoy Economics with its modeling, but really relished her semester of introductory high school physics as a 9th grader. She's a more 'applied math' mathy kid.
Does that help?
