Bandits

A kid runs away from boarding school to watch the cave where a bunch of bandits hide. The bandits discover and chase him but the kid escapes. He returns to the school but it's been destroyed. He's the only survivor and decides to wait for help. Some days after, a group of wild kids enter the school and take him with them. He becomes a "bandido" and will revenge the destruction of his school and the killing of his friends.