Earlier quoted context omitted.
The very humble comprehensive I went to in Scotland addressed this issue with streaming - which seemed to work pretty well. Is streaming out of fashion in state schools these days? I know its alive and well in public schools as my son was streamed. Edit: For those outside the UK: public schools are a type of private school.
What's streaming?
You break kids up by test score and then put all the top kids together, all the middle kids together, and all the bottom kids together. My public school experimented with it for one year, but reverted. Rumor was, parents felt like their kids were being written off in the 6th grade.