Seeker, teacherwith2kids whose comments are always reflective and knowledgeable pointed out that the percentage which might really need teaching separately is the top one percent or fewer. It is a vanishingly small number.
The top ten percent is actually quite a number of children and contrary to what has been said, perhaps on another thread, i think it would make quite a difference to the school community. To say that moving the top ten percent makes no difference is to ignore the contribution these children make to the community.
Matthew Parris wrote recently of a visit to a JCB sponsored school which was very technically/vocationally oriented. It impressed him against his expectations and it sounded very well thought out.
There is no answer that is best for all. As Talkinpeace said somewhere, you can speak to top educationists in any country and nowhere will you find one who claims that given a tweak here and there, their country's as things broadly right.
Other countries have different social beliefs - one which believes in social cohesion will be less keen on elitism. (I think Scandanavia and The Netherlands come under that description). Some of those countries cited admiringly in our current concern with 'getting on' have clear hierarchies which I find saddening when i have actually lived among them.
I don't have an answer, but I don't think there is one.