I don't have a problem with Grammar Schools in practice because, quite simply, there just isn't a valid replacement at the moment that will be able to maintain the same sorts of standard in academic education. On the other hand, the principle that everybody's life and career path should be largely determined at the age of 11 or 12 is surely something we should be rejecting. I'm sure we all know examples of people who didn't quite get engaged with education properly until long after arriving at whatever High school it was they went to -- or, equivalently, people who were incredibly bright to start with but then sort of fizzled out for some reason later on. Whatever system we have in place for education, it has to be able to easily cope with these sorts of children, who are hardly uncommon. One such example might be a friend of mine,who would probably have, by his own admission, fallen under TTT's definition of "disruptive scum" -- but then got his act together around about the time of A-levels (perhaps helped by being reasonably intelligent anyway), went on to university, and is now working towards a PhD. I don't think that this would have been realised when he was arriving at High School, although it's hard to know -- but surely any system that effectively brands people for life based on how they are at 11 is broken in principle. Yes, there's always the opportunity for late switching back and forth (eg add a 13+ and a 15+ r something) but such upheavals in life, school, friends etc are also disruptive.
Seems to me, therefore, that we should be working as hard as possible to make grammar schools essentially redundant -- but, in the meantime, getting rid of them is self-defeating as long as the standards provided there simply aren't so readily available in the rest of the education system.
However, I do wonder if this entire argument is a little too stuck in the past anyway. The educational establishments of the future may be far more oriented towards being online as opposed to in some fixed building, where (if people can organise it properly, at least) the sort of educational standards that are available in the past only to a select few can now be shared across the world to thousands at a time, and then again. We're still some way away from this, but perhaps we shouldn't be so religiously adherent to the idea that some sort of physical building to host a school is essential.