Battle Royale(2000)

Japan at the start of the new millennium. The country is in a state of chaos, violence by rebellious teenagers in schools is completely out of control. The government hits back with a new law: every year a school class picked at random will be cast away on a desert island to fight it out among themselves. The rules are simple: it lasts three days, everyone gets water, food and a weapon and only one may survive. Then a class on a school trip is kidnapped. When they wake up, angry teacher Kitano tells them that the collar around their necks monitors their position and can be caused to explode remotely at any moment.