Posting this for general discussion. Maybe you’ve used EMF/IMACS or are curious about it.
https://www.elementsofmathematics.com/ (the first 30 day lesson module is free.)
It’s a special and semi-controversial curriculum that focuses on 1970s-style “New Math”, a college/professional pure math approach to the K-12 curriculum, and skips a lot of the easy/boring/applied material and the material that K-12 teaches but isn’t needed for college and grad school, and skips the hard puzzle problems that AMC/AIME+AOPS emphasize.
Then they tack on a quick Supplement to cover the Common Core standards in a few days at the end of K-12 equivalent year.
It starts with “prealgebra” in summer after 5th grade and finishes “precalculus” end of 8th grade, feeding into 9th grade calculus. (You can start wheney you want, and it's self-paced.) But the real value prop is that the students are already speaking the language of upper level undergrad pure math, and covers the basics of college Pure Math 101/102 topics like number theory, set theory, formal logic, basic group/field theory.
The material is presented in order of Prealgebra+Algebra+Algebra2, then Geometry+Precalculus
It achieves that extreme acceleration by starting early, and focusing on the formal theory and intuition, in a kid-friendly presentation format, and skipping "mathematically unimportant" side topics like, um, trigonometry apparently, and doing sophisticated topics at an easier level of problem complexity than something like AOPS does.
AOPS does less formal math but much harder problems, for competition-prep (but a lot of AOPS students don’t actuall do the hard problems in AOPS class.). Doing both of these styles of enrichment would be quite intense but immensely rewarding for an interested student, and probably would be worth spreading out over more years.
Once you start the free module 1, you can see a full detailed table of contents at
https://www.elementsofmathematics.com/eimacs/tocemf
The mebsite also has a pretty detailed listing of topics too.
If you want to do this at home or in a special independent study at school, you can buy the $900 4.25 year subscription to the online curriculum. You can pay a little more for a pay as you go, quit when you want, ($60 per module, 17 modules after free 1.) (You can’t buy just the upper half if your kid is already skilled in Prealgebra, algebra, geometry basics. And there are no paper books).
I did this program as a student in school with live teachers, many years ago, before AOPS existed. It was 10x more fun and interesting than regular school math. It was a bit different then; It was spread out over an extra year then, and included a formal mathematical computer science component (in Scheme/LISP),and it had two concurrent tracks for intuitive background and rigorous formal symbolic logic proofs of the theory.
At the time, they didn’t have the Common Core supplements. so I had to fill in or just skip the missing pieces on my own. When I switched back to regular school in 9th, I self-studied during the summer, and took a placement test to pass geometry and algebra 2, to place into precalculus.