For some reason I really hate the idea of setting, and it annoys me it is so prevalent in schools. I think the reason is I've always felt I fell victim to the unfair side of setting when I moved schools at 15. I was set for atleast a B in Maths buts when I changed school I was placed in a set that was destined to sit the intermediate paper where the highest possible grade was a C regardless of how well you did - needless to say I got a C.
The fact is when you use setting a line has to be drawn somewhere, you can only fit so meny kids in a class and if you miss the cut based on numbers....
I think if we dropped the idea that everyone must study certain subject and used effective streaming to match pupils ability and interests with subjects then there'd be no need for setting and kids would naturally perfom better because the are not being forced to sit subject that are no use to them.
I also think effective use of setting plans, teaching assistants and focusing on individual pupil lead learning, with pupils helping each other, will make setting obsolete. Setting is a product of league tables and teacher lead learning by rote.