Just coming back and thinking about DS's remark.
After the mock, which floored several of them because they are top set students used to finding the majority of each paper relatively easy (and the school then used very high grade boundaries, so the grade interpretations were possibly on the low side), the school has plied them with 'extremely hard' mock-type papers, just to get them used to really struggling.
So DS and all his set have gone into today's exam expecting it to be really, really hard and with strategies to cope with that. So DS's calibration of 'OK' will be 'no worse than the practice papers', which means '* impossible, especially the last couple of questions.
It's been a hard few months, but at least I feel that DS's work ethic and attitude has had a good workout! Now he's reversed his decision about taking maths into the sixth form, i feel, regardless of how he does in the end, it won't have been a wholly bad experience - perhaps cushioning the jump to A level, tbh.
However, if this is top set in a good comp, i am sending masses of thoughts to those for whom maths is anyway much more difficult. i hope the foundation papers were OK.