[SoftwareMaven]

Kids forget. If you just introduce a concept, spend a day or even a week on it, then move on to a different concept, most kids (if not almost all) will forget it by the beginning of the next school year.

Personally, it think the time for manipulation of symbols has passed. Math should be only about concepts and hardware or software should do he manipulation. But then you run into systemic issues like "how do I test all students". The factory-styled learning environment needs to die.