The War Game
Krig (original)
When 11-year-old Malte moves with his mother to a new neighborhood, he quickly finds himself in a feud between two rivaling gangs. His cunning and skill helps him find a place in this new world. But his methods also serve to escalate the conflict, and it's not long until war is inevitable.
Watch "The War Game" from streaming services Plex Free, Amazon released in 2017. It's a action & adventure and kids movie, and has a rating of 6.3 out of 10 from Imdb which is usually fine for this kind of movie.