Georgimama is right - we used to live in Southend which had both comprehensives and grammar schools. Pupils did not have to take the 11+, and I have no doubt that there were children who decided not to sit it, but who would have gained a place at the grammar schools had they done so.
All of my ds's sat the 11+, and two passed high enough to be given places at grammar schools (they kindly chose different ones so that we had to get two lots of uniform etc), and the third didn't pass high enough, so was given a place at our catchment school, which is a comprehensive school.
We felt that the grammar schools had higher expectations of their pupils academic standards and behaviour - and in fact, for me it was the behaviour aspect that swung me towards the grammar schools. I believe that a teacher who has to spend a significant amount of teaching time simply getting the class to behave and listen, is not going to be able to teach them as well as one whose pupils know that they are expected to sit quietly and work - and it was my perception of our local schools that this was far more the case in the grammars than the comprehensives.
Now we've moved, all the boys are or will be going to the local comprehensive, and I am very happy with that indeed. This school has high standards of work and behaviour, and expects a lot of its pupils. If our local comprehensive in Southend had had similar standards and attainments, I would have been more than happy for all the boys to go there.
Dh and I have always chosen what we believed would give our boys the best possible ecucation, wherever we lived. Does that make us 'aspirational parents'? Perhaps it does, but surely that's a good thing? Are there any parents on here who do not aspire to the best education for their child? I doubt it.