All the waste comes from making available an education to those without the ability or willingness to learn.
I agree with you on the willingness to learn part. You can have the best teachers and schools in the world, but if a child does not want to learn, you aren't going to teach him anything. I have always thought there should be an opt out point where high schoolers can opt out of further classwork and sign on for vocational work study or something similar.
On the inability to learn, I tend to disagree. Every child can learn. They are certainly not able to learn the same things or learn at the same pace, but they can all learn. Severly disabled children can learn how to take care of themselves or how to interact and communicate.
I think that these children are entitled to an education just like children without disabilities. It costs alot because it can be very specialized, but it certainly far less than the cost of institutionalizing these children which is what we used to do. Many can and do learn how to take care of themselves and some can even participate in specially designed employment programs. There is no such thing as a child who is unable to learn.
I always try to remember that every child that is unable to obtain employment which is sufficient to support him/her, will end up costing society a whole lot more in the long run. The goal of public education should be to give every child the maximum ability to provide for themselves.