Angelina, I am not sure St Olave's was a "one-off" - I am guessing plenty of grammar schools doing something like that. My professional experience is that many schools may encourage some students to move on at end of Year 12 not for league table reasons, but for best wishes of student - a view the student may not always take. (PS: I was using the worn "culling" somewhat ironically, which I now realise is never a good idea on social media)