You sound like a brilliant teacher. At my DC's secondary school I got the impression (possibly unfair) that the ethos was, 'Work hard and we'll support you. Slack off and you'll be dismissed as a wrong 'un'.
DD was advised to consider dropping one of her Scottish highers (roughly equivalent to AS levels but used by Scottish universities to offer places) after a poor prelim result. This would not have affected the school's stats because of the way they're measured in Scotland - data is for 3+ highers and 5+ highers but it would have limited DD's choices hugely. Fortunately she sat the exam and got an A.
DS got 4xA and 1B in his highers. Which was great, but the B was unexpected - as were a couple of the As - and he was one of quite a few pupils who didn't do as well in that subject as their prelims and teachers' reports suggested, which does make me wonder if there is a problem in that particular department. Btw not English or Maths. Things like these, unfortunately have a demotivating effect on both my stubborn and rebellious DC.
It can't help when the exam system is so complicated, with assignments etc contributing to the final grade. I sometimes think some of the exams are a test of organisational skills, which is unfortunate in the case of my DS.
I completely agree with you in principle, but as a parent I wasn't willing to let my 17YO's very important grades suffer because of his lack of organisation. TBF he does have a diagnosis of slight ASD which doesn't help. Unfortunately the senior management who bend over backwards to support pupils to get into Oxbridge and medicine, were unsympathetic to his small, but insignificant extra needs.
When HE was free I was of a let them fail - and learn from their mistakes mindset - but now I think it's such a hugely expensive lesson to learn that I made huge efforts to chivvy my two along.
FWIW, IMO schools are asked to do far too much. Teach in complicated ways without text books, provide huge amounts of extra-curricular activities, cover everything in PSE, have policies for every last teeny tiny thing, do ridiculous paperwork, cope with disruptive children and demanding parents. Unfortunately they sometimes get my back up by participating in the 'modern' culture of selling themselves by 'bragging' about their achievements, obsessing about uniforms etc, while failing to address important problems such as drugs being sold on the premises, horrendous sexist language and inappropriate use of mobile phones etc. No wonder so many teenagers have mental health problems. Gah, it's all so complicated.
In principle I agree with you though 