Khan academy did studies on it, and came up with this result, after you complete questions, you have to wait fifteen hours to make sure you have learned the skill properly. You can't get around it, you just have to wait.

If this is a review experience for my students, reflection would not have the same result as with a student who was experiencing these objectives for the first time. I agree with students having a time lapse for introduction, practice and mastery of "new" objectives; however, that does not apply for review of past mastered objectives. For the purpose in which I am trying to use this system, the wait time limits my students production on mastered curriculum. At this rate, it will be mid-year before my students can confidently say they have mastered 6th and 7th grade objectives in preparation for my 8th grade curriculum.

You could just recommend the skills they have to review.
There is no limit on practicing a skill.

Mine randomly locked me out for seven hours. I had not had a long streak of correct problems.

I think khan academy should create a review system that teachers could enable for students. Then if enabled, mastery challenges wouldn't have timers or you wouldn't have to practice skills. I don't know but i'm sure they could find something that worked.

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