Stats - always interesting and usually don't tell the full story. Two more questions which could be asked are: why do those with a Chinese background do the best, and how do those worst performing in education, the white working class, score in the tests.
As a general observation on who applies and whether it reflects society: if you're joining the armed forces, you have to be prepared to kill whoever at the behest of the government of the day. You might be against harming others or killing per se; you might be against killing specific nationalities. It's unlikely, therefore, to be a representative cross section.
Just my 2 bob's worth.