I don't have much to add to what I've said already, save a couple of observations:
Why are grammar schools co-opted into a framework that advocates parental choice when, as Oliver Kamm points out, grammar schools represent the opposite? It shouldn't be necessary to point this out, but obviously it is: with academic selection, it is the school that exercises the choice, not the parents.
I suspect the answer lies in the assumption of success - which is to say advocates of grammar schools assume their children would pass the 11-plus. Only inferior children from inferior families would have to send their children to inferior secondary moderns.
This is probably what is behind the 70% that Stephen Pollard claims answered in the affirmative to the question as to whether there should be more grammar schools established. I don't know but I doubt any of them answered with the understanding that their childrens' attendance at these schools was by no means guaranteed.
Like all opinion polls, it depends on how you frame the question. Perhaps they could try asking, "Would you like to see three secondary moderns established in every town?" and if this were coupled with the understanding that their children had a good chance of ending up in one of them - I suspect the results might be a little different.
Update: If this(pdf) is the poll Pollard was referring to, it is 70% of Tory voters that favour grammars, not - as he misleadingly suggested - the public as a whole.
Also from the beeb:
"David Cameron says it is "delusional" to talk about bringing in more grammar schools, as Conservative rebels are doing in calling for a policy U-turn.He could have added that it was Thatcher who closed more grammar schools than Labour ever did. Ignoring the 1922 reactionaries: dunno if Cameron is doing this because he's clever or simply out of instinct but it's the right thing to do and Labour should be worried.
He told a Westminster press conference there was a "fantasy element" to the debate, saying they had not built new grammars during 18 years in power."