I could rant all day about the injustices of the 11+ system (which is what I always call it, not the "grammar school system"). And that's despite the fact that I passed the 11+ and in theory should have benefited from a "grammar school education". Unfortunately, it didn't suit me at all because it was assumed that a) if you were bright, you were academic and b) that the academic is superior to the practical. Also the British system suited the clever specialist, not the clever generalist, and still does to a large extent.

It was just possible to make it to university if you failed your 11+. I met a couple of lads at the technical college where I ended up retaking my A-levels who had both gone to secondary moders schools due to failing the English part of the 11+. Both were excellent at maths and probably these days would have been diagnosed with dyslexia and given extra help at an early age. However, if it hadn't been for their parents backing them to the hilt and getting them to leave school at 16 and transfer to the local tech where they were sailing through physics, maths and further maths (and desperately struggling to pass the O-level English needed to get them to university), I don't know what they would have done. Ended up very frustrated, most probably. But as you say, a comprehensive school with setting would have provided for their educational needs much better, as well as allowing me to keep doing the practical subjects I enjoyed instead of just fast-tracking me through the academic ones.