I, just recently, escaped from the public school system in Georgia [USA], and I must say it was a nightmare.
Zooter is right: Rather than filtering out the dumb kids, schools have been forced into lowering their overall standards so that more people can meet them. I went through high school in accelerated classes, and also had my fair share of the "regular" classes. although the advanced classes tended to be more tame, both were unruly most of the time.
I have a cousin who teaches in high school somewhere in North Carolina. As we all know, there are 2 basic kinds of students: the ones who want to learn [aka "Smart kids"] and the ones who really dont. She was told, not by the principal at her school, but by the school board, that any student who was doing well should be put into a group of 3-4 students who weren't doing well, in an attempt to bring the other students up. While a good idea on paper, all it did was hold back the students who wanted to learn.
With that said, rather than trying to lower standards, we need to raise them and push kids to learn. A college degree has become the new high school diploma because getting a diploma from a high school isnt an accomplishment anymore, and that needs to change.