As others have mentioned, AoPS is a great resource and is used by many kids that accelerate in math. I think the problem will not be if your child can do Alg I, the problem will be the issues of keeping them challenged if they get accelerated too far.
After reading, The Calculus Trap, by Ruscyzk, we slowed DS down by having him take several of the AoPS courses like Number Theory and Counting & Probability. It worked fine for him as he likes math. He is now in 8th grade and doing independent study taking AoPS PreCalculus. We buy the books for him and he works through the books and then he does the online course. He likes this method of reinforcement.
There are quite a few kids on the same path as DS but unfortunately not at his school. He is friends with them through a local math club. It has been difficult to keep him challenged/interested as he typically works alone in math.
