Indeed. All I see here, is an aptitude-driven advancement system (Kahn) coming into conflict with an age-based advancement system (public schools).
Clearly, if we're to reap the benefits of an aptitude-driven advancement system, we need to erase the core assumptions of the public school curriculum. (age-based peer groups, pass/fail an entire grade at a time, etc)
When students are permitted to progress in different subjects at different speeds, the desire to see "brakes" put on tools like Kahn's will evaporate.
we need to erase the core assumptions of the public school curriculum
Great, I agree. Why do you think these assumptions are so hard to change? Who are the people holding the assumptions? Why haven't they changed their minds already?
We run into problems not only with the established educators, but I think also from parents. A lot of people tend to get really edgy when you're discussing changing things like curriculum or pedagogy, because they're very risk averse when it comes to their children. Not all parents are like this, but a lot of them are. They're also generally bad at properly evaluating their kids' strengths and weaknesses since they tend to have a positive bias.
That, and there's the 'education as hazing' notion: "If I had to suffer through four years of high school bored out of my mind, so should the next crop of kids! It's good for the little buggers! Builds character!"
Frankly, the best way to deal with that mindset is to invent some crap for the people who have it to go through so they leave the rest of us alone. Maybe call it a team-building exercise.
Clearly, if we're to reap the benefits of an aptitude-driven advancement system, we need to erase the core assumptions of the public school curriculum. (age-based peer groups, pass/fail an entire grade at a time, etc)
When students are permitted to progress in different subjects at different speeds, the desire to see "brakes" put on tools like Kahn's will evaporate.