More anecdata: my kids are just finishing Y7 at a comprehensive school in an area where we have access to a handful of some the finest superselective grammars in the country. They go to a school where every student takes a foreign language at GCSE (and has done so since long before the 'EBacc' was a political football - because the head thinks that every young person has the right to be taught a language up to the age of 16, even if they might not ace an exam in it); where there is no setting or streaming; where they have been treasured throughout the whole of their first year; where they have learnt how to be competitive with themselves, not others; and where I can email any of their teachers, at any time, and get a thoughtful, enthusiastic response within hours. Where they can take drama, or dance for GCSE if they choose (neither is offered at the grammars - although, of course, such fripperies are catered for through extra-curricular productions of an extremely high standard).
The facilities are a bit shit, actually. It's struggling to balance the budget. And on paper, its results are awful (but only because students are allowed to make choices about when they take exams - the results students actually leave with are well above the national average). There is disruptive behaviour; there are some deeply troubled kids there. The teachers don't have an easy ride (unlike those in the grammar schools, who happily claim that they'd 'never go back' to teaching in a non-selective environment) - yet they still manage to inspire their students, and their energy, commitment and enthusiasm are incredible.
Our kids didn't take the 11+. But I can be pretty confident that, had they done so, they'd have been offered places at the superselective (their SATs scores were higher than any of the kids from their old primary who passed in their year, and also in this year - all of whom had tutoring for a minimum of two terms). And they'd be having a super time there, and come out with some pretty damn shiny results.
I don't regret our choice for a moment. But we are bloody lucky that the comprehensive round the corner happens to be as brilliant as it is. And I hate, hate, hate the fact that families round here are forced to make such hard, limiting choices for their children. My best friend has three children. Her oldest was born right at the end of August; he just failed to scrape the 11+; her middle one was born right at the start of September - he would have been one of a very few 11-year-olds taking the 11+ when he took it, and he just scraped a pass. Both of them are bright, keen boys, with supportive parents, who would be a credit to any school they were in. It's loopy.