I suggested it to my friend who has a gifted 9 year old, says he moved through three years of math in 3 weeks before moving at a more normal pace on hitting algebra. I saw her demo it a bit, looks like there's a well developed skill tree of individual competencies and then a carefully designed algorithm to assess mastery of those competencies and revisit on an optimal schedule using spaced repetition. From what I saw, responses are multiple choice, which I think could lead to some gamesmanship from brighter (craftier?) students and them selecting the correct answer from the available responses but not able to actually arrive at it on their own. The program seems to be producing all sorts of outliers, with a few dozen 8th graders (and some younger) getting 5 on Calc BC- an extremely rare event nationally. My stupid guess is that this is probably a valuable program, but you may want to supplement a bit with non-Mathacademy problems just to verify your child can transfer the skills learned to non multiple-choice questions.