Short trousers Frederick? They used to come down to the knees and then the thick socks, would come up to the knees. Only bit exposed would have been the knees and they would have been covered by that gabardine mac wouldn't they. That is how I remember it, although being a girl. AND we girls didn't have tights when I was a girl, they were not in the shops in the 50's and early 60's*, so we had skirts, also to the knees, and then short socks, so really the boys were better off than the girls.
Must have saved families a fortune having boys knees exposed to the elements, I realised when my boys would put their knees through within days of getting new trousers. And I would patch, neatly with knee patches, and they'd hole them too, but as I could never have kept up financially with this regular damage to their clothes it was the only way.