Salman Khan’s free math and science videos have moved from YouTube to classrooms, reports the New York Times, which looks at a San Jose charter school that’s using Khan’s lessons — and student-tracking software to teach ninth-grade math to students at very different levels.

(Teacher Jesse Roe) can see that a girl sitting against the wall is zipping through geometry exercises; that a boy with long curls over his eyes is stuck on a lesson on long equations; and that another boy in the front row is getting a handle on probability.

Each student’s math journey shows up instantly on the laptop Mr. Roe carries as he wanders the room. He stops at each desk, cajoles, offers tips, reassures.

The Khan-enabled classroom makes it possible to target instruction to each student’s level, while mapping each student’s math comprehension for the teacher. While some see Khan’s mini-lectures as too “sage on the stage,” the net effect is to turn the teacher into a “guide on the side.”

Diane Tavenner, chief of the Summit chain of four charter schools, turned to Khan to teach the fundamentals after small-group problem-solving proved slow and unreliable.

Khan Academy remains free, thanks to foundation support.

The interesting thing about Khan’s model is that Khan himself is so good at teaching. The guy has a real talent for teaching math.

I wonder.

Khan’s love of math is obvious and comes through clearly. It’s also implied strongly in the large number of lectures on math relative to many other subjects. But a real talent for teaching math?

If you’re enthusiastic about the subject and limited to ten minute, or thereabouts, chunks of time how tough is it to be effective?

I’ve done a bunch of Khan Academy lectures and I’m not so sure Sal Khan’s a great teacher, in the vein of say, Marva Collins or Jaime Escalante, as he is the lucky recipient of an advantage those teachers never enjoyed – Youtube.

The economics of instruction requires lectures to be rather longer then ten minutes it being an unjustifiable expense to have the lecturer show up in person for only ten minutes. Sal Khan isn’t saddled by that requirement. He can “umm” and “so you see” quite a bit and still not lose the listeners interest because there’s not that much to sit through. Alternatively, if he’s knocked out a real snorer he can just record a replacement using the previous lecture as a guide to what not to do in its replacement.

What’s under-appreciated is the test/tracking software which adds a significant component to the perceived value of Khan Academy. That may, in fact, be more important then the lectures since by giving context to the lectures in a graphic representation of progress through the “learning space” allows for the perception of progress. That’s no small thing since the feedback to the learner is part of what impels further learning.

Anyhow, I expect a lot more such announcements since the advantage to everyone – students, teachers, administrators, school operators – is so obvious.

I know some kids who’ve had wonderful experience with the Kahn and teacher-in-the classroom combination. Instead of replacing a good teacher, it lets a good teacher work more effectively.