Even if Khan is truly liberating students to advance at their own pace, it’s not clear that the schools will be able to cope. The very concept of grade levels implies groups of students moving along together at an even pace. So what happens when, using Khan Academy, you wind up with a kid in fifth grade who has mastered high school trigonometry and physics—but is still functioning like a regular 10-year-old when it comes to writing, history, and social studies? Khan’s programmer, Ben Kamens, has heard from teachers who’ve seen Khan Academy presentations and loved the idea but wondered whether they could modify it “to stop students from becoming this advanced.”
Thats our public education system for you in a nutshell. Perhaps "No Child Left Behind" should be changed to "No Child Moves Ahead".