We have gone the Art of problem solving route (after school) with our DD when faced with a similar dilemma. Before that we used Singapore Maths which she just tore through. She is already whole grade accelerated but the Maths just doesn't move fast enough. We are not in a position to homeschool so this has been the option that has been optimal for us. We have been lucky in that she has had teachers that have allowed her to do some of this coursework in the classroom. Scheduling an in school single subject acceleration can be a royal pain if the school's timetables do not line up resulting in missed classes and catch up work at home too.
Best of luck!
