Our kids spend too long sitting in class being taught things they already know or can learn on their own. Teachers spend too much time lecturing to the class and the lowest common denominator, rather than focusing instruction on those that need it.
The simplest example is the Kahn Academy - which is entirely self-paced and student led. But there are other more customisable and teacher-led examples, like Promethean's self paced learning.
When I think of all those young minds waiting for the lesson to catch up or who are too scared to ask for help; I can't help thinking that something must be done.