I second blackcat.

Pre-algebra (up to 8th grade), most gifties have a sense to do it without instructions. But some geometry questions (in 6th-8th), you can't do it if you do not know the formula.

With my DD, I used Thinkwell. I let her do the chapter tests. If she gets >90, I let her skip.

Khan Academy is free. It used to be free flow tree pattern and kind of confusing but now they have grade levels which will help your DD a lot.