Would it be possible to use Khan Academy as a complete math course? I'm asking primarily for my dd (15) who will be in 11th grade next year. She has used Chalkdust since pre-Algebra, is math minded, and does well with it. She really enjoys Khan Academy though and asked about using it as a stand alone as she thinks she would progress more quickly. (She often understands the concepts quickly enough that watching the Chalkdust videos isn't all that engaging for her.) I'd still have her use the Chalkdust test prep course.
Goal-wise, her top interest is ballet and her second interest is math. Science, bacteria primarily, are her third area of interst. Clearly, her math skills need to be strong.
I have other children who will be in Algebra I and Basic Math next year. I might have them start using Khan as a supplement for now.