Oh dear, I really feel the need to defend the school a little here.
In the last newsletter, the school confirmed that of the last gcse cohort, 95% had achieved at least 5 A*. Now I think that's a pretty amazing result and science and maths can't account for all of those A*. Even if English isn't up to scratch when some of the girls enter the school, it obviously doesn't prevent them achieving when it matters!
To be fair Running Mum, the school did try to remove the catchment for the last set of admissions, but the uproar from locals was so intense that the school was forced to reinstate it.
Also, Tiffins has for some time now excluded girls who "failed" their test from applying again. In their case, you are deemed to have "failed" if you don't achieve at least the score of the final person to be admitted to the school. At least for Nonsuch, you only have to achieve the mark which is deemed to show you are of selective ability. Many girls who achieve this mark may not get offered a place (eg not in catchment and not in top 80) but at least they will get a second crack of the whip.
I agree though that upping the requirement to remain in the 6th form seems harsh