plowens

Greetings fellow film nerds.
I've been after the title of this film for so long that I think I may have dreamt or imagined it.
As a child I recall seeing a 50s or late 40s film in which a german-jewish imigrant father and young son are introduced in to a british community.
The boy makes freinds with an english boy called John, who has to deal with his other freinds antipathy to his new friend as they regard him as a nazi and fail to realise that as a jew, he is anything but. The film concludes with the group of boys (who are members of a youth army organisation with rifles but no bullets) enacting a mock firing squad execution which goes tragically wrong, as real bullets are mistakenly handed out and the german boy is killed.
Please help as this is doing my head in.