There is a big difference in the grades students are getting in the UK. I don't have an answer as to why but here are some examples for A level Chemistry. The links below give the tables with GCSE and A level exam results from 1993 to 2016.
In 1993 16.8% got an A and 10.3% a U
by 2016 8.4% were A* and 23.5% got an A (31.9% at A/A*) with only 2.7% getting a U.
In 1993 16.8% got an A and 10.3% a U
by 2016 8.4% were A* and 23.5% got an A (31.9% at A/A*) with only 2.7% getting a U.
http://www.bstubbs.co.uk/a-lev.htm
http://www.bstubbs.co.uk/gcse.htm