I suspect seeker's suggestion that the middle grade students fare worst in the selective system is probably true. My stepfather always talks about his experience of going to a sec mod (obviously yonks ago) and that it was brilliant for someone like him who got to be top of the sec mod (just failed 11+ and would have been a second set student in a comp) and his confidence was boosted accordingly.
One point, however, is that years ago when there were only O levels and CSEs, it was a tough thing to be stuck in the wrong half of the system if you would have matured and done better later but wouldn't, for example, even be taught the same subjects. And the same has again recently been true for many students where if 'stuck' in a sec mod then there wasn't the same access to separate science or languages, or being 'encouraged' down the BTec route etc etc, and this is obviously unfair if a child is capable of much more academically but just had a bad day on 11+ day or, indeed, blossomed later.
All this is an indictment of the selective system (as well as other things - I don't want to be accused of only focussing on the able child).
However, I do believe that when we're discussing comprehensives as the alternative, we all must acknowledge that they're not one homogeneous lump in which all is equal. Some comps (maybe with a more deprived intake or a smaller intake in a rural area) also do not offer the same quality of education as the best comps in the best areas. Some have been pushing easier qualifications onto bright students because there are still not enough top students to warrant triple sciences etc etc.
There has been a recent Ofsted investigation (or ongoing) into why some authorities with the same type of system (comp) and the same profile of population vary so wildly in their outcomes and this is very interesting.
pugs I really don't understand your argument that selective and sec mods schools compete for your business and comps don't. Surely competition amongst schools is predicated entirely on surplus places, availability of transport, parental income - to move house - and aspiration and entrance criteria? (Might have missed some)