I was sent this chart, which after looking at the school site, shows the 5 A*-C results:

I really don't like this representation of the data - the upward arrows are confusing and the fact that intervening years are greyed out, makes me think that something "odd" is going on.

Poking around on the web site you can find the raw data:

Some things I've tidied up - the years into the final year, the scale from 0 to 100 (no lie factor), no gridlines, no arrows and added data labels.
The story is the same, less clutter and more focus on the data.