British, run by some fantastic people from the University of Cambridge. Arguably there is no institution with a better reputation in this domain. I did some front end and back end work for them over a decade ago and there's definitely some good mathematics in there. Their mission is to enrich mathematical learning for all levels, but there's plenty of content designed for gifted teens.
I suggest looking outside the US for a curriculum. The nation that came up with the terms "precalculus" and "prealgebra" surely has a pessimistic view on the value of elementary mathematics. The ideas do not exist only to prop up calculus and algebra!
British, run by some fantastic people from the University of Cambridge. Arguably there is no institution with a better reputation in this domain. I did some front end and back end work for them over a decade ago and there's definitely some good mathematics in there. Their mission is to enrich mathematical learning for all levels, but there's plenty of content designed for gifted teens.
I suggest looking outside the US for a curriculum. The nation that came up with the terms "precalculus" and "prealgebra" surely has a pessimistic view on the value of elementary mathematics. The ideas do not exist only to prop up calculus and algebra!