I wasn't sure either. At the beginning when 'old' Bert was being interviewed, he said "I remember what they did to my teacher."
The women all jumped when there were several noises, one of which sounded like a vehicle horn. We only saw Joe and the other teacher waiting for the bus, inferring that Mr Eyre was shot, but I cannot recall hearing of any conscientious objectors being shot, only people who became frightened on the front line and refused to go over top.
Loved the way the Dad his his horse in the pub!