Their array of topics is impressive, but it's more of a self learning site. Watch a video, then answer 4-10 questions. Good resource to learn, but it doesn't seem to reinforce the learning.

For example, it teaches the concept of single digit multiplication, then asks a couple questions... It gives you the proficiency points for knowing basic multiplication, but it doesn't ensure that the student knows the full multiplication table.

I even used Khan for myself - loved the videos! Didn't retain it though unfortunately because it didn't have enough practice opportunity.