A much worse feeling was knowing that some of the students did not understand my talk even though I thought I had done such a fine job. That can be the worst, most frustrating part of teaching. Even if you ask a group whether they understand, few in the group will have the courage to say no and waste everyones time. That is one problem with one-size-fits-all teaching.
Salman Khan wants to use video to reinvent education. He might already have done that. Years ago in my former school board, there was a concept kicked around called "mastery learning." Basically students don't proceed until they have mastered a particular objective. So imagine a student airline pilot who only gets 75% of his/her landings correct. Though thats not bad, you would not want that person to become a pilot, not yet anyway. The problem with mastery learning is that it does not fit the model on which most school systems function, and since there is little competition among school systems because they are largely government institutions, well, you see what I mean. Students are left with gaps in their education, not able to master some things because of time or some other constraint. Salman Khan has helped flip the eduction system around. Using hundreds (2100 so far) of YouTube videos to teach basic concepts, Khan has allowed students to master by repetition (YouTube is very patient) particular lessons so that they may proceed to the next level fully prepared. Teachers can then use one-to-one contact to help the stragglers. Does it work? Well, have a look the TED video below and he will explain it, then visit the KhanAcademy here.