My hunch is attitudes towards teachers in the UK probably correlate fairly closely with how well people did in exams. An issue with instrumental justifications for education is if you don't do well then you've 'failed' which is obviously going to cause resentment.

Also as @michael_merrick has pointed out, by making exam results so high stakes for life chances schools in which children 'fail' are quite logically resented by those who went to them.

And given finite grades (which is quite right) a LOT of people will feel schools and teachers have failed them. The answer might be:
A. Don't moralise academic success. Make it clear dignity is inherent.
B. More opportunities for lifelong learning so school isn't as high stakes

C. Create curriculum of inherent not just instrumentalist worth. Allow pupils who don't do well in an exam to still feel the subject was interesting and a worthwhile use of their time.

This actually does mean rethinking some of the ways schools work. E g: not good enough to discourage a child from picking a GCSE subject just because they aren't likely to get a high grade.