I am a high school math teacher and I use Khan Academy as my curriculum in the classroom.  I have seen an article in the Knowledge Base called "Why did Khan Academy build a new mastery system?" that indicates that "The new mastery system does not yet include review questions (aka spiral review), but it is on our product roadmap to introduce spiral review questions into students quizzes and unit tests to help reinforce concepts they may have learned earlier."  I actually really like the new mastery system because I can easily teach and assign material by units, but it has been a significant shortcoming in my teaching this year to not have any review incorporated into regular instructions or (especially) assessments.  Can we have an update on where this is in the process "on our product roadmap"?  Is it expected to be live in time for next school year?  I would love to see this as soon as possible.