Poorly thought out
Your child has to pass the mastery test with 100% accuracy and speed 2 out of 3 times to move from one operation to the next. This idiocy results in a fourth grader who tests into accelerated math never moving off of single digit addition. I am not sure which educational philosophy advocates staying in the same place FOREVER until you are perfect not just once but several times. Do your child a favor and go straight to Kahn Academy if you want them to actually learn math.
#s guy about
XtraMath, v3.16.3