My eldest is doing an Algebra 2 class with AoPS.
There are things I really like about AoPS, but based on my experience with just this class, I'm not sure that it can replace a traditional course in the subject it covers. From what I've observed, AoPS is really good for giving challenging problems once you understand the basic ideas. But my son doesn't really get a lot of the basics from his class. We use a classic textbook authored by a guy named Richard Brown for the basics.* So I wouldn't really talk about AoPS in terms of not being able to go back to a regular math class. Well, the kind of math class I run, anyway. DS had to sit through a regular math class for six weeks last year and he was tearing his hair out over it.
Have you thought about EPGY or CTY?
*ETA: The Brown books (he wrote four, from Algebra 1 to Advanced Math) also provide a lot of challenging problems. IMO, they're some of the best high school math textbooks out there.
Also, will your son's teacher let him study math independently? Getting my son there took a lot of effort.
Last edited by Val; 12/23/12 08:37 PM.