The preponderance of officers and NCOs in the group won't reflect the overall make-up of the Erdington unit of which they are all a part. These men have been on a Home Guard weapons training course – artillery guns, anti-tank weapons etc – and they will tend to be men in the unit with a degree of authority (and perhaps a responsibility for passing on their new knowledge to others when they rejoin the unit).
There is so much interesting detail in this image. For example, look at the number of men with Great War experience, shown by their medal ribbons. Survivors to a man. 25 years earlier several of them would have been in the trenches, hoping they would survive and enjoy a lifetime of peace. Just 25 years earlier – the equivalent, for us, of 1994 and to me the day before yesterday. And now here they are, back in uniform, for Round 2.
Chris