Where's yer grammar? Upstairs - were's yourn?

Apparently the go-ahead may be given for the first new grammar school for 50 years. I've had my say on this before (see 31/5/07) and I think once again we are missing the big question.  We shouldn't, in my opinion, be talking about the pro's and con's of grammar schools and the 11+ selection system. What we should be discussing is why the comprehensive model hasn't worked the way it was supposed to.  There was nothing wrong with the theory, so why has it not worked in practice? If it had, there would be no need to be talking about new grammar schools.