I have lots of friends who are teachers here in the UK. The only metric that they really care about is whether or not their pupils achieve a grade C or higher at GCSE (age 16).

A very high level of effort is focused on D/C borderline students as a result, with more or less able students more or less abandoned. The ROI from moving a D to a C is [perceived as] far greater than moving a C to a B.

So much for actual education...