TheThird yes, the awards system isn't very well-judged!
I doubt they finally realised that DS is the overall highest achiever. His teacher is numerate enough to be able to notice that when he looks at a list of class test results, DS always has the highest score. He will know that marking DS's maths tests, is just tick, tick, tick etc. The teacher never, ever has to assist DS in class. So, he has known for a long time.
As to the timing, its strange to do it now when DS really doesn't care. 14 months ago, it was a different story. Back then, I could see that DS was ready to give up on maths altogether because he was finding lessons so boring. I emailed the teacher acknowledging that he couldn't change the lessons but asking him please just find some way to encourage DS in maths so that he doesn't give up completely e.g. a word of praise. The teacher emailed me back to say of course he would do that, and then failed to follow through (until now). The attainment award at the end of year 10 would have been any easy solution.
I solved the problem of DS's disengagement from maths without the school's help.
Anyway, DS will go and collect the award, but, its a shame it couldn't have come at a time when he was struggling.