There is absolutely no question, IMO, that education has been 'dumbed down' massively over the years (state and private), so I am not in the slightest bit surprised at the findings of the trainee teacher.
Children are taught to pass the exam, in a grammar school this is now aimed at passing at A*/A and no less, at GCSE certainly. If they think outside the box, or write too much, they are at risk of getting a lower grade, and they are told this.I find it quite extraordinary (and depressing).
At grammar schools, certainly, the staff have learnt to play the game, inform the pupils and, hey presto, they all get top grades now (as they do in the private sector) What about the schools where the teachers aren't prepared to inform the pupils of what they need to do, there is a possibility that there are bright pupils who aren't getting the grades they deserve, quite possibly by doing too much rather than not enough.
In very simplistic terms, I actually think if A levels (and possibly GCSEs) were made much harder it would be better for all.
Getting a string of A*s would be the exception rather than the norm (as it is becoming in many schools) and the vast majority of pupils would be in the 'average' ability and the teaching would be tailored thus. It would stop the discrepancy between the private/state sector where distinctly average pupils in some schools come out with all As and in other schools, those same 'average' pupils, come out with much lower grades. It would also stop those who really are not very academic coming out with a set of worthless GCSEs in worthless subjects, just for the sake of the league tables. Those children could actually be taught something worthwhile and useful for their futures, instead of being fooled into thinking a grade D in Tourism or something is actually equal to a grade C or above in Physics, for instance.
At the other end of the scale, there are some students getting top grades in some subjects who could easily work to a much higher standard who have been awarded the same grade as someone who has not really understood the subject but who has ticked all the right boxes and regurgitated the right facts.
At the moment the education system is failing those at the top and the bottom of the scale.