I went to one - my choice in part, parents would have preferred me to go to the Catholic secondary. As a teacher I have worked in two.
I know if I had gone to the Catholic school I would have coasted (even more than I did).
Some people seem to he very against the grammar school system and I'm not sure why. It was the making of my dad (miner's son from council estate in Scotland)and I think that all counties should have that provision. Surely it's just split site streaming in a way.